[GadgetKen]

Originally Posted by adam917

Correct me if I'm wrong but, from what I understand Jolt/Beyond GSM are an AT&T MVNO that has similar or the same coverage AT&T PAYG service has (just the native network) and Tuyo is a T-Mobile MVNO that has no roaming either.

I keep my T-Mobile To-Go line active due to their roaming agreements (and dropped my AT&T PAYG line due to their lack of them, not to mention other crap) around North America (including Canada & Mexico). It's also nice to get _some_ Internet access (and MMS) even though it is extremely limited. Of course it sucks that one is charged to receive SMS/MMS, though I believe it is cheaper than even Simple Mobile when used only for SMS/MMS in NA.

Correct on both counts. Both the Jolt (Beyond GSM/Beyond Wireless in Ohio went bankrupt and Jolt/N.E.T. in California took over their accounts) and Tuyo sim cards are MVNO's limited to the native networks of their respective backbone carriers.
Advantages are cheaper rates per minute for domestic (with promotional discounts Tuyo is about 7 US cents a minute and Jolt is a flat 15 cents), heavily discounted international rates, and with the Tuyo card, the ability to use the sim card balance as a calling card. Since my primary interest in these 2 cards is inexpensive voice and occasional SMS, it works for me. Jolt is more expensive per minute than Tuyo but has coverage in areas that Tuyo does not(in a dual sim phone I'll look at which sim works, has a decent signal, and has a cheaper rate).
Disadvantages are refills are not as widely available (use the internet for that), nickel and diming for receiving text messages, neither have comprehensive data services(Tuyo only has download store and MMS; Jolt has neither), and they can't roam on other carriers in the US or other countries. But since I've got the ekit Simple Calling sim, a Digicel Bermuda sim, unlocked GSM phones, a satphone, a 3G wireless USB data key, and a wifi phone I'm pretty much covered for my communications needs (all right, it's probably overkill, but I like options).