Let the hive mind of Engadget get that for you.
"As someone who doesn't reside in the USA, I was wondering what would be the best way to get internet for my computer in the US for a couple of weeks? If it were Europe I know I'd look for some prepaid data. Is there anything similar offered by American carriers? A MiFi or a data SIM that I can tether from would work, but I'm trying to maintain a tight budget. Help!"
Personally I think a Wave App Store is the lamest thing I've heard about Wave period. Google is all about keeping things free in exchange for all your data. So why would they charge for 3rd-party extensions? That would be like Firefox requiring you to pay for plug-ins and themes. In a tech world headed more towards open-source this is quite disconcerting to hear.
As for Live Typing being turned off- you either like it or you don't and personally I think that is what makes wave unique, it forces you to think a little bit before you just type something; also lets you see how people think!