I'm on T-Mobile (testing) w/some startling finds. $1 a day? Hell yes!
Now, before I go into this small little review of mine, as ALWAYS with T-Mobile and the iPhone, you go into it KNOWING that you are going to lose speedy service. A/k/a? Edge only, no 3G.
With that being said, I purchased a prepaid kit from a T-Mobile store, set it up on the Sidekick prepaid plan, got the SIM card and got to my car. I pop that little bast@rd in, got the service working. Phone call quality is automatically better than AT&T. Why? Because I can ACTUALLY MAKE A CALL (I'm in NYC, where 1 out of 2 calls are dropped. I can attest to this!)
So, the calls are working, and the unlimited SMS messaging is working, as it comes standard with the prepaid plan. (I know because I neurotically kept calling #999# to check my available T-Mobile balance.) However, my e-Mail and internet were not working, along with almost all of the apps on the iPhone, and a quick research session on my laptop unveiled the fact that T-Mobile had caught on to the fact that millions of iPhone users were coming on and using the Sidekick plan for their iPhones (without paying for the postpaid "Smartphone" plan T-Mobile offered for the iPhone). So, in short, they modified the original Sidekick plan to have certain features and functions not work with the Sidekick prepaid plan.
But I want my internet and e-Mail, g0ddamm!t!
So once again, more research (I can't stress this enough, RESEARCH IS YOUR FRIEND, it will WORK WONDERS, as long as you aren't retarded!) lead me to the following site -
Now, I am not advertising anything about this site except that they more or less, for a fee, set up a proxy server specifically for your iPhone (I ordered the $9.99 per month plan, personally) where basically, everything works. Your e-Mail, internet, YouTube, iTunes, AppStore, Twitter/Facebook, etc... it all works - albeit on the Edge network, so yes, it WILL work, but it will also be a bit slow.
The customer service reps who I spoke to were EXTREMELY helpful. The process is not difficult at ALL, you download and install (directly from your iPhone) a mobileconfig file after they create it for you. THEN, you have to set up a time with them (keep in mind, they're located in Arizona) and you will have a 15 minute time window to take the iPhone you want to use, and visit a link they send you via e-Mail. They capture your IP address, add it to their private VPN server which was set up for you and you alone, and voila - all your sh!t works, just as it should.
I DID run into a few problems. For example, I attempted to use my "GV Mobile+" app (for the free SMS feature, and a familiar # my contacts would recognize) and it simply would not load. The reason for this, after speaking in depth with the website customer service reps, is because very few (almost NONE, actually) apps released on Cydia have support for proxy servers. That means no VPN support. Almost ALL App store apps have proxy support, so they will work.
So to test that theory, I fired up Skype (while using 3G Unrestrictor, of course), and attempted to make a phone call.
It went through. Barely. But not because of software or hardware conflicts, but simply because the Edge network is too slow to maintain a decent call quality. There were lots of echoes, and a good amount of feedback as well. The call didn't drop, I killed it. Violently.
So ultimately, if you are savvy enough, I'd ABSOLUTELY recommend that you give my methods above a try. It's a pretty sweet deal to pay $1 a day (plus phone calls at $0.15 per minute) as compared to AT&T's $4.66 per day.
Ultimately, I'd rather pay about $45 per month for the iPhone than $145, no?
Cliffnote: As much as I hate to do it, I DO intend to go back to AT&T, but ONLY because I want their 3G speed, and ONLY until Verizon gets the iPhone, which is looking more and more plausible each day, especially now that the Verizon CEO has gone on records to state that Verizon wants it. HOWEVER, I only posted this tutorial / review mainly because with the way the economy has been lately, and just students in general, not everyone can afford a $145+ cellular bill every month, and T-Mobile may be the best way for that to go down. I happen to be lucky, because my profession thrives on hard times, but not everyone else's does. This is just a way to save you guys some money. I genuinely hate AT&T, I just want to make that clear. I would actually subscribe my iPhone to a goat if it had better service than AT&T, but unfortunately, AT&T's data (which is really all I use the iPhone for) is just simply top notch.