Approach with caution. Some folks are reporting problems upgrading from previous versions of Ubuntu, e.g., Dapper Drake, to Ubuntu 6.10 Edgy Eft. Others are reporting no problems.
Since Dapper Drake is Ubuntu 6.06 LTS (long term support), I will probably stay with it for a while on systems that I rely on.
I may experiment with Edgy Eft for fresh installs and systems that aren't critical.