It should be quite speedy. Might have to adjust your VM settings. Dont go overboard with it. Give it like 8mb ram for video card, and 1gb for ram. If you give it too much ram it'll choke off OS X which in turn will slow down the VM. Same goes for too little. Chromium needs a good 800mb ram alone just to run decently. Also when using a VM on low ram machines, close all other heavy applications in OS X to free up system memory.
Cheers