I will assume you are talking about after 11.10 (Oneiric) has been released - as per this question, it's pretty buggy.
This is highly subjective, but I always do a fresh install, for a number of reasons:
Ubuntu gets somewhat bogged down after 6 months.
A fresh install (as opposed to a upgrade) keeps possible dependency conflicts to a minimum.
I like playing with new shiny features without having old configs/packages around to screw up.
How do I do it?
- Download release via torrent, seed for a few days (I'm running Ubuntu+1 by then anyway)
- Once I notice that demand has dropped off, I create a new folder on
/home partition and call it something like
Stuff I need to
- I create my bootable USB key.
- I install.
- After that, I boot into my new install, and start transferring data
from that directory I made earlier.