Sites and Services - Routing Groups

[redwhip]

Hi

Would somebody please help me to understand how AD Sites & Services and Exchange routing groups co-exist. Are they totally independant of each other?

I have 3 AD sites and when I setup a user mailbox at one site it takes ages to replicate even if I instruct it to replicate now. However it does replicate eventually.
Each site has one domain controller which also runs Exchange 2003.
There is a 512K link between each site and message flow seems OK.
All internet mail arrives and departs via site1.

Should I consider using routing groups as well? What advantages would this provide if I do?

Thanks

Red