I really haven't noticed any difference in speed or compatibility with sp2 running. The thing is with Microsoft, at some point, you are almost forced to go to the next level since they will no longer "support" earlier support packs. In fact, you probably have sp2 components running under your sp1. It is better to switch to the later support pack for no other reason than when sp3 comes along, it will presume that sp2 had preceded it.