I would check the memory usage.
Coming from mainly windows environment, my biggest complaint about mac is initial ram requirement is fairly big.(almost a gig to just boot up). On top of that, application do not completely quit itself and remain in memory(I am assuming so that it will launch quickly again).
I have macbook 2009 and I always keep my close eyes on the memory usage. I would think single biggest thing you can probably do is upgrade memory to 4 gig. Other than I love the macbook....