I needed something that would replace MS Exchange for managing my calendar, address book, and emails. I am currently doing my own thing and not working for a firm that has Exchange and I currently use a Windows Mobile device, not a BlackBerry. I was pleasantly surprised to see that Google has done a pretty good job so far.
Once you do the basics (setup gmail, Google calendar, Google docs if you'de like) you just need to setup Google Sync for your mobile device (for calendar and address book) and configure your device to connect via IMAP with gmail. You should use IMAP instead of POP if you can, it's more secure and more efficient. Now everything is in sync. The only thing that (I don't think) you can sync currently is the todo list.