i use an acer laptop based system running synapse orion plat 7 (and more than likely ableton live 7 soon)...with a focusrite saffire sound doohicky and occasionally playing live i use my roland TB 303 and TR 707 synced up with a BOSS se 700 multi effects (best kept secret in acid techno...well....it was till i just said it ;) )
never had many problems with timing...although a regular power source that wont trip my focusrite is always a major mission....nothing worse than the massive sound of....SILENCE! lol...it depends how lazy i am really...and i dont like humping the equivalent of a jean michel jarre gig around on the london public transport system LOL