You can buy a capacitive touch pen for like $5 that will write on any capacitive touch screen.
It works for the palm pre's display.
You can also get a nice leather protector case with a pen slot to hold that pen. Also the screen is much bigger and more sensitive, and if you want to use Graffitti, install Classic, the Palm OS emulator, onto Web OS.
You are right about external storage, it sucks, but then just wait... larger internal storage models of the pre will be out. I mean, if it has 32 gigs, would it really matter if it was external?
There are apps you can install on your Pre and computer to sync data with your computer directly, but its a little bit redundant because the Pre syncs all of your contact information and data through the internet, aka "cloud computing", a simply google account or Micro$oft exchange account would solve that.
Its better than syncing to your computer because then your data exists in three places potentially
1)synced to your computer
2) synced in the 'cloud'
3)synced on your device
If that isnt enough, Palm automatically sets you up with Backup Storage called your Palm Profile. Every day your phones contacts, mail etc is backed up on their servers for you. If you brick your device, when you reinstall the OS with Web OS Doctor, (which automatically fixes your phone for you) it automatically puts all of your data back on the phone. off your account.
So, I wouldn't go with the Pro. I had a Treo 700wx, both you and me know how Win Mo sucks. Not worth it.