After more than four years, AT&T’s exclusivity on iPhone in the U.S. has come to an end; the iPhone 4 is coming to Verizon on February 10th.  Some questions remain unanswered: Will the antenna issues that plagued the iPhone 4's AT&T launch last summer also be a problem on Verizon's network? Will the differences in the AT&T and Verizon networks mean differences for iPhone users?  Based on all the news reports and first look reviews today, here is what we know so far about the iPhone on Verizon.

What's different?
In terms of hardware, Verizon will have almost the exact same device. The major difference is the CDMA chips inside the Verizon iPhone that will allow it to run on Verizon's network. On the outside, the most eagle-eyed observers will notice that the Verizon iPhone 4's ringer/mute switch on the top left side has been moved slightly downward. Apple says it was done to accommodate the CDMA chips on the inside, and consequently iPhone 4 cases and bumpers currently on the market will not fit correctly.

The Verizon iPhone's software is slightly more advanced too: it's running iOS 4.2.5, while the most current release for all other iPhones is iOS 4.2.1.

In terms of wireless service, CDMA technology currently does not allow voice and data to be sent over the network simultaneously, which means you can't, for example, make a phone call while checking e-mail or using the maps app. The CDMA Development Group has said this will change for all CDMA operators sometime this spring.

One feature Verizon will offer that AT&T does not, though, is the ability to use the iPhone as a Wi-Fi hot spot. Verizon says up to five Wi-Fi devices can connect to the iPhone's Internet connection at the same time.

How much will the Verizon iPhone cost? 
Verizon is offering the iPhone 4 for the same price as Apple, AT&T, and others: $199 for 16GB, $299 for 32GB. Both include a two-year contract.  Nothing has been said yet on how much the monthly data & voice plans will cost.  

When can I buy it? 
If you're a current Verizon customer, congrats, you get first crack at it. You can pre-order it starting February 3. The rest of us have to wait until February 10 for the official launch.

Do I get a free bumper case with this iPhone 4? 
Sorry, no. Apple ended its guarantee of a free bumper for all iPhone 4 customers at the end of September.

If Verizon is pushing its 4G network so hard, why is the iPhone still using Verizon's 3G network? 
Apple's Tim Cook said there were two main reasons that the iPhone isn't on LTE: the first generation of LTE chipsets "forced design compromises," and "Verizon customers want the iPhone now."

Can I use my existing AT&T iPhone 4 on Verizon's network?
Unfortunately, the iPhone 4 that is designed for and sold by AT&T will not work on Verizon Wireless' network. The reason is that the AT&T iPhone is based on a technology standard known as GSM, while Verizon Wireless uses a technology standard called CDMA. These are different technologies, and they are not interchangeable. So if you want to use the iPhone on Verizon, you'll have to purchase the new CDMA iPhone 4 designed specifically for Verizon Wireless.

Will I need to sign a new contract? 
Yes, unless you wish to buy the iPhone 4 at the no-contract price, which typically costs much more up front. Again, the 16GB model will cost $199 with a two-year contract; the 32GB model will sell for $299.

Do you think that there will be a mass exodus from AT&T's network to Verizon's network for the iPhone 4?
While it would come in handy, we have no have no way to predict the future however we don't think that there will be a mass exodus from AT&T to Verizon Wireless. While there is significant pent-up demand for the Verizon iPhone, I think that most of the initial customers will be existing Verizon customers. These are likely people who are loyal Verizon subscribers.

There are also lots of subscribers who abandoned Verizon for AT&T to get the iPhone. There is a good chance that Verizon will win some of these customers back. And Verizon could also win customers from Sprint Nextel and T-Mobile USA--those who wanted the iPhone but were unwilling to go to AT&T because of the network issues.

But given the fact that the Verizon iPhone is essentially the same phone that has been offered by AT&T since June 2010, I don't think that existing AT&T customers who are moderately satisfied with the AT&T service will jump ship yet. For one, a good portion of these customers, especially those who just bought the iPhone 4, are still under contract.

What do you think AT&T will do to compete with Verizon? Will it reduce data service prices? 
The new competition for the iPhone is also likely to put even more pressure on AT&T to improve its network. Now that the iPhone is also on Verizon, AT&T's biggest rival, AT&T will need to find new ways to compete more aggressively with Verizon. AT&T is improving its network, but just how quickly it can add capacity and improve reliability is crucial, as it competes head to head with Verizon. Again, this level of competition is great news for consumers because they will likely see continued improvement in AT&T's network performance.

Do you think that Verizon's network will be able to handle all the new iPhone subscribers?
Verizon's executives say they are ready for the iPhone. Verizon Wireless CEO Daniel Mead said during the presentation Tuesday that Verizon has been working with Apple since 2008 to develop an iPhone for its network. He said the network has been tested, and he is confident that consumers will continue to have the same reliable service with the Verizon iPhone that they have come to expect with other Verizon devices.

Verizon Wireless Chief Technology Officer Tony Melone also said in an interview with CNET at CES last week that the network is ready.

"I feel very confident about our 3G and 4G networks," he said. "We have seen tremendous growth over the past 18 months on our network with the Android devices and other smartphones. We are adding more capacity to the 3G network in 2011 to meet whatever demands customers put on us."

When will a 4G LTE version of the iPhone be on the market?
That's a good question. Again, this is just a guess. But based on what Apple has done in the past, I think that it will be at least a year before Apple puts LTE chips in any iPhones, regardless of whether they are made for AT&T or Verizon. (AT&T is launching its LTE network this summer. And Verizon launched its LTE network in December.)

I think that Apple will wait until the LTE chip market is more mature before it puts them in iPhones. There are two reasons for this. First, the cost of those chips will drop considerably over time and will reduce the cost of producing the devices. And second, I think that Apple also wants to wait until all the kinks on LTE devices have been worked out. I expect LTE smartphones to have some battery life challenges. Apple is all about creating the best overall experience for consumers, and that requires a satisfactory battery life.

As you may also recall, the very first iPhone worked on AT&T's 2.5G EDGE network, even though there were already plenty of 3G handsets on the market. It took Apple another year before it introduced the iPhone 3G.