We bought a couple of Net10 phones this trip (March 12 2011) following the tips here. I bought them at Publix (they are at the customer service desk). I got the last $15 LG standard handset, and had to pay $20 for a Samsung flip phone; 2nd cheapest option. No free air time offered at this time, so add $30 for a 300 minute card. Apparently there is a $20 card, but we couldn't find them there or a couple of other stores we checked. Add 6% state tax for total purchase price.
Activation was relatively simple, but does require an Internet access. The salesperson had indicated that it could be done from the handset, but the instructions provided do not support this. Note that one advantage to 300 minutes is that the activation period is 2 months; less than 300 minutes only last 1 month. Note that Net10 merged with Tracphone - our LG turned out to have been repackaged. No problems related to the brand change however.
Service was marginal. In our resort (Vistana) we had no issues making or receiving calls. At the Disney Parks, we had a couple of non-connections, but most calls completed. At Universal Studios, service was horrendous. Over several hours both of our touring groups tried calling the other group several times (probably about 25 attempted calls) with no ability to connect. Note that you are charge 1 minute for each of these failed calls - only a dime each perhaps, but adds insult to injury. I think that this was a Net10 service issue, as many others around were talking on their cells without issues. Luckily we managed to run into the other party as we were making our way to the exit; no easy feat in the Universal complex!
International dialing was not as good as advertised. At activation, they indicate that international dialing should take about 3 days to start. You need to dial *1 (send) 1 for English, then enter the long distance number. We activated on Sunday, and finally got our first international connection on the following Saturday evening at the airport as we were leaving. Prior to Saturday, international calls gave us a fast busy, but did actually ring the receiving phone. SIL had her Rogers phone with her, so if she got a strange ring, she knew to call us back.
Overall, I give Net10 about about a 50% grade - barely passing. I still like the idea, but would probably spring a bit more for phone with a major carrier. I may also consider jailbreaking my Android phone next time and getting an ATT SIM card for it instead.