I prefer the fresh install myself, and with the home partition separated
out it's fairly painless. Upgrade is for quick and dirty only.

But look, if you've gone up to 10.10 then it's still in its first Alpha
isn't it? Certainly a long way from release. There's large disclaimers
on the download page about how it's not finished, and not to use it on
production machines. Give it a fair crack, wait till it's officially
available before criticising it