I don't use straighttalk, But I do use net10 which offers the same deal. I started the 1st if this month and so far everything is going well, unlimited talk/text/data. Contrary to the straighttalk unlimited terms which are very vague on specific limits and such, net10 puts it in clear terms, they give you 50,000 minutes a month for talk/text/data. Obviously, calls deduct from that on a minute by minute basis. Texts use 0.5 minutes I believe, and data I haven't quite figured the conversion, it may just be mb to minute. In case you didn't look it up out of curiosity, there are only something like 43,000 actual minutes in a month, so you should be good.
As of today (12-31-12) I have used 8:39 of talk time and about 2.5 GB of data with no problems. I got the Net10 package which came with 3 sim cards-a Standard ATT sim, a Micro ATT sim, and a Standard T-Mobile sim. I cut the Standard ATT sim down by hand following a guide here and make sure you print out the template on A4 sized paper if possible.
This sim card pack can be bought from Target locally as well as Best Buy (Note I have no affiliation with either, nor with Net10. I am just a happy customer)
Also posted below are a few speed tests from the Pittsburgh PA area as well as all the way down to Orlando FL (Vacation Drive).