I started the switch a couple years ago and it was a pain until I got a replacement for all my 18v tools, but couldn't be happier. They have an adapter now that would ease the pain.
[Link: dewalt.com]

Have you seen the new 60v tools and batteries? The batteries are compatible with the 20v tools and you get 4x the runtime. I've been eying the 60v stud/joist drill!

[Link: dewalt.com]

Dave, If your kit has the 2ah batteries, get some 4 or 5's for the circular saw and recip.