Minecraft Performance/OptiFine in Linux Help

I'm trying to get Minecraft to run fluently on my netbook. According to the community specifications, I should be able to play the game fluently; however, with stock everything I was getting <1FPS - 8FPS. I've done some tweaking, including installing SimpleCraft, using Oracle JRE 7 up25, and turning down details to the lowest, and my performance is much better, but what's killing me is the total lack of consistency. I still get anywhere between 7-60FPS (usually rapidly fluctuates between 12-36FPS). >~<

I've tried installing OptiFine, but I get an error about invalid or corrupted jar file. I tried following the instructions exactly, but they were vague on where to put the class files.

Any tips on either increaseing Minecraft performance, or getting Optifine to work?

Specs:

Linux Mint 14 x64 (Gnome Classic)

AMD C-60 (1GHz/1.33GHz Dual-Core)

2GB DDR3-1066

Radeon HD 6290 (276MHz/400MHz - Proprietary drivers installed)

maybe use majic launcher and install optifine using that should for!