How does the gmail Android App compare to the Webmail experience when using multiple gmail accounts? This is a "pre-sales" question as I don't currently have an Android device. I did try out one when Android was version 1.6, but was dissappointed. I am interested to know if 2.2 or 2.3 is better. 

In particular, I use Gmail as my only email client. It operates all my email accounts (3 corporate and 2 personal). Every email is sent and received via the gmail server and is therefore filed and searchable in gmail. When I compose and email, I can choose which account to send it from and it comes via the domain server (i.e. not from gmail). 

My impresssion of android is that is can set up seperate email (pop, imap etc) inboxes and operate them directly with each domain server as pop/imap - but I don't want that as emails will not be kept on the gmail server and therefore filed, backed up and searchable from the webmail client. 

How does email account aggregation actually work in Android - is it true Gmail Webmail handling or is it just multi-account handling direct with domainemail servers missing Gmails servers in the process?

Thanks
Just use the GMail app and not the Email app.  You can select what email to send from -- it shows all the addresses you have set up in GMail -- and has a surprising number of GMail's features for a mobile app.  It does go through GMail's servers and you will have your archive.  I don't think you can set up and manage POP accounts from it, but if you're not abandoning the web interface entirely then it doesn't matter.