I have a Nexus, and my wife has an EPIC. She says it is the best physical keyboard she has ever had (BB, Samsung Moment, etc.) I think it lags as well, and her battery life is awful. She doesn't seem to mind, and has simply gotten used to plugging it in whenever the opportunity presents itself.
She doesn't mind the Touchwiz. I don't think she really cares. The keyboard was what she wanted, so that's what we got.