I currently have the Droid X , Droid Incredible, Fascinate, and Droid 2 Global White. Out of the box all of the Droids are preferable to the Fascinate unless you plan on rooting. Out of the box the Fascinate has quite a bit of lag even with alternate launchers such as ADW and Launcher Pro. The GPS on the Fascinate is a crap shoot, some work ok but many don't. I have also found call quality and signal strength to be better on all the Droids as well.
There is supposed to be a new update to rectify the Fascinate issues that should be coming out soon but I would wait and see if the update does in fact rectify the issues before you try it out. Also keep in mind that all the Droids run Android 2.2 but the Fascinate is running Android 2.1 and we don't really know when the Fascinate will be getting the 2.2 update.