In austria currently, I've had good luck with 3 (drei.at) service. Cost was a bit higher than I was expecting, perhaps the sales clerk took advantage a bit with the language barrier. I got the 1 month unlimited data package (nimm3 internet flat), final price was 31.59 euro, 37.90 with tax.

Anyway, works fine with my huawei E586 mifi, speed is good, not sure about coverage outside in the countryside, as I'm only in tourist areas where you'd expect good service. Even streamed a couple hours of netflix over a vpn connection with no buffering issues.