Okay, need I say more..... so let it rip:

10) Runs on Windows, Mac and Linux of different flavours too. Everyone can help.
9) *We* are part of a winning team.
8) Diversity of projects, with option to select preference and backup assignment.
7) Work always ready for download from top notch servers, little lost crunch time waiting for work.
6) Helpful message board community
5) Scientist give regular progress and development updates (would have liked it on #2 spot!)
4) Active and responsive project support.
3) Graphics help us understand how it works in UD and BOINC agent
2) *We* control what *We* work on and when.
1) Great mission with all results available to the public domain at no cost.