If you are talking about installing Yosemite DP1 right now, I suggest making a separate partition. That way, if you have a problem, you still have Mavericks and can easily delete the new partition or reinstall Yosemite as different builds come out.
At this point, Yosemite is buggy, because it is a preview and not in beta release. Don't expect the programs you want or need to use will work in Yosemite. Make sure you back up your HD before installing a new OS.
Continued a long streak of problem-free updates since the day I got my MBP, which was at the end of Leopard's life. Includes both DPs and stable releases alike. But I'm probably on the luckier end I reckon.