Want the newest YouTube app on your 2.1 Fascinate? Then check out the XDA-Developers thread on how to add it. Simple enough to do.
1. Remove current YouTube app through adb.
2. Install new YouTube app through adb or package installer.
3. Enjoy.
Obviously you will need to be rooted for this to work.
XDA-Developers thread:
[MOD] Youtube 'Gingerbread' ported to Eclair - xda-developers