I have not given 10.10 a serious spin yet, though I've noticed the longer (and slightly squirrelly) startup behavior when running it in a VM. My plan is to bring my work desktop up to 10.04 and my home desktop up to 10.10 in the very near future. (Work is still back on 8.04 believe it or not, and home is currently on 9.10.)
I almost always do full reinstalls instead of upgrades. While serious breakage on an upgrade install is fairly rare, the last time I did an upgrade there were some little things that didn't seem quite right. It's not like you need to worry about product activation, so "nuke from orbit" every time you move to a new version isn't unreasonable.
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