I went to a cell store (Active Cellualr) in Silverthorne Colorado which is a AT&T dealer, said I had a Iphone 3GS and wanted the GoPhone sim. The sim const me $20.00 and the bought $25.00 of air time on the pay as you go plan 10 cents a minute calls and 20 cents a text.

I did not get the data plan, after each call or text you get a free text message from GoPhone with the cost of the text or call and your current balance.

Flew to Regina, the phone switched to Rogers automatically, worked great charged me the higher internation rates 39 cents call and 25 cents text, got to Winnipeg, the phone again went to Rogers automatically, phone wored great, still get the balance messages from Go Phone.
Once home in Winnipeg, switch back to Speakout. At 88 days, I'll add another $25.00 to keep the sim active for another 90 days.
cheers! - ken

The phone worked great in the Summit County area, worked great in the Denver airport,

Word of caution...I used to be with Telus and when travelling took their International Plan. Went to Mexico for one day and never used the phone, but forgot to turn it off. It got cloned just from walking down the street, Telus cut me off because they noticed suspicious activity, and when I got back found out there was $4,000 in charges.

I did not have to pay of course...but it was that easy.

Too bad my iPhone 4 is locked to bell and cannot take this option , not planning to US anyway.

I went to an AT&T store (in Mall of America, Minneapolis) and asked to sign up for their Gophone $2 a day unlimited voice/text plan . The sim card(in my case, a micro sim for my iphone 4) is free but the min voucher value you can buy is $15. This is valid for 1 month. You can also buy a $25 voucher good for 3 months or $100 voucher good for 1 year.

He activated the sim in the store so no number to call when you insert the sim in the phone.

I later bought their 100Mb plan for data for $15 – expensive but I really wanted to be able to surf and use the apps on the phone. They also have a $25 /500Mb plan and a $5 /10 Mb plan. I logged onto the Gophone website and bought the data plan online using my credit card.

I then updated the APN setting on the iphone using the website http://www.unlockit.co.nz. I selected the AT&T profile for Cingular as I had read online that is one that works. I emailed myself the config file and installed it (after deleting the Speakout profile as you can only have 1 profile installed at a time). I was on wi-fi network, of course, to be able to do this.
After turning 3G off and then on (I think I booted the phone as well), the new APN profile worked and I was able to browse at 3G speeds,

I could have bought the data plan in the store, I suppose, and they may have been able to help me setup my iphone but I didn't add the data plan until later that day…

The AT&T clerk neglected to tell me that calls to Canada are an additional 19 cents a minute in addition to the $2 daily charge. But no additional charge for texts to Canada.

Overall the service worked well for the short time I was in the USA and worth the $30.
I selected Gophone because it seemed to be the only one that offered data with their plan in the US.
Maybe T-Mobile offers a similar service but I knew AT&T network would work with my iphone...

Anyways, I was able to surf even as we were driving across North Dakota where the Gophone coverage map seems to indicate service is spotty…