HI, I just bought a Nexus S this morning from Best Buy and then went directly to a T-Mobile shop for a PrePaid plan. It's the end of the day, and my experience was quite painful but finally I'm good, so I think I'll share. First I took the "good" plan for $50 for 30 days (Unlimited calls and texts) with 100MB of data. There is a $10 activation fee, and in 5 mins I was ready to go with my phone. Now after the initial sync from Google, I had already used more than 60MB from the plan. So after 2 hours I went back to the shop to change to the 2GB for only $20 more ($70 for 30 days). BE CAREFUL: It's impossible!! I needed to cancel my $50 loose it all and repay $70?? I call T-Mobile Customer service, manager and so on: No way! So, finally she told me that when my 100Mb are used I can used the web2go Web DayPass for $1.49 a day unlimited data!! What? Basically for less than $45 per 30 days I get unlimited, but for $50 I get only 100Mb ) Makes total sense! So, I was happy, I moved back to "Pay as you Go" plan ($0 per month), put $100 credits to reserve the number for a year, and think that I'll pay $1.49 every day I want to use the web. Sounds great! Two hours ago I finally reached my 100Mb and my data from all apps stopped. I tried to go the web to activate the Web DayPass: No way. I called and there is no way to activate it from the web, and no way to have the t-zones running on Nexus S. So I was stuck: No data! Finally ready the T-mobile FAQ I found that tzones will pop up in the web browser when I used all my data to the last byte. So, I browsed, and browsed until wap.t-zones.com popup and ask me if I want Web Day Pass. I said yes, and it now used my $100 credits for my data usage. Conclusion: I pay as I go for unlimited data. It was hard, T-mobile sale reps are totally ignorant on the subject, but I'm OK now.