Bluetooth is real sweet if you get a compatible cell phone.
I have a crontab setup on my laptop that syncs all my contacts, calendars, and notes each night. I stopped carrying a PDA and now just use my cell phone for everything.
It's also nice that if something happens to your phone everything is backed up on your laptop.
A 17" laptop isn't bad to carry. Mine is 17" and actually weighs much less then the 15" that it replaced.
Get a good bag for it. This is what I use.
http://www.booqbags.com/Detail.bok?no=21