Glad you found your way back here. The site was attacked. But we don't need to dwell on that now. Dave checked in a little while ago and he's doing well with his TC1100.
If you've already done it, then all you'll get from me is a genuine - "I hope you enjoy it and it serves you well".
Take a look at some recent posts (last couple of days in the HP forum) about the TC4200/TC4400.
You've got your whole routine setup around the external batteries you've already got. If you are okay with the performance with your Tablet PCs, I'd wait.
I just found most of your old posts in here.
click the cached page links.