I had a Sony/Ericsson T610 with T-mobile and liked the phone very much. It's small, light, has a build in camera, nice color display, and most importantly bluetooth. If you're not already using a bluetooth headset you will be soon, and once you start using one you'll never go back. Anyway, T-mobile is GSM based (as is AT&T and Cingular), so my phone works all around the world, which is handy, but it doesn't work in lake Tahoe as the GSM footprint in the US is small compared to the CDMA footprint (used by Verizon and Sprint).
So, since the FCC mandated that you must be allowed to transfer your phone number from one carrier to another, I decided to test it out and move my cell number from T-mobile to Sprint. The only problem was that Sprint didn't have a bluetooth phone. With a little research I found that Sony/Ericsson does make a CDMA bluetooth phone, but Sprint doesn't actively support or advertise it. So I custom ordered the Sony/Ericsson T608 and ported my number to sprint.
The porting process is initiated with your new carrier, they cancel with your old carrier and handle everything from there. If you have a contract with your old carrier you'll still be on the hook for it, so you've got to watch this carefully.
The T608 arrived in the mail and there was nothing else I needed to do until the switchover, which was seamless: they give you a time at which the switchover will occur, this one was Sat at 5:42am, and at that time it just happens automatically. Calls show up at your new phone, the new phone is live and the old phone stops working.
However, it quickly became clear to me that:
1) Sprint didn't have that great of coverage at my house in Tahoe, and
2) The Sony/Ericsson T608 is a POS. The display is smaller than on the 610, there's no camera, it's bigger ... and the bluetooth doesn't really work. The sound over the bluetooth connection was always crackly and Sprint didn't make available a synchronization client for the phone -- so I would either have to buy a data cable or enter all my contacts by hand.
Well, Sprint does have a 14 day cancellation policy so ... I found that Radio Shack was carrying the new Motorola v710 phone in limited quantities at special stores. This phone has bluetooth and works on the Verizon network. So I called around ‘till I found one, paid for it over the phone before someone else got it, and ported my number from Sprint to Verizon.
Again, the porting process was seamless. The only hiccup was that they told me it would happen at 5-something p.m. but it actually happened at 11 something a.m. But, again, there was a teething problem apparent with the bluetooth. Motorola makes you spend an extra $30 to sync their phones via bluetooth, so I pay the fee (T-mobile + Sony/Ericsson just worked w/o no extra SW to buy), and spend all weekend banging on it to no avail and support isn't open ‘till Monday. I find out on Monday that there is an upcoming over-the-air firmware update for the phone ... and until then sync won't work. So I managed to at least get my $30 back (and keep the SW), the update is scheduled for "end of this month of first week of next month". We'll see.
So I can't sync my contacts but the bluetooth sound quality on the v710 is better than either of the Sony/Ericssons. Plus it has a megapixle camera with light/flash that also takes video, 10MB of built in memory, a memory expansion card slot, two color displays ... It's a sweet phone. I'll really like it when it sync's.
In the end, wireless number portability is super easy to do and works great. I've done two ports in less than two weeks and have had no problems. When your contract is up, you owe it to yourself to at least get a free/discounted new phone. Go ahead and port your number, it's almost fun.