The RemoteApp vs Terminal Server latencies should be pretty close if not identical but I didn't do any testing between the two however so I can't be 100% - the bandwidth utlization in theory should be close because with RemoteApp and TS, the server is just broadcasting the screen video, user controls and print data.
If you've never tried RemoteApp, once you do, you will NEVER go back to TS. 
It is a much cleaner experience for the user since they only see the application as if the client was installed locally. Biggest benefit is that its easier to secure the server from inadvertant changes because the user doesn't see a desktop.
Our WAN speed is half of what yours is, but we typically have less than a 5 second delay before a print job starts. We are currently using Win2003 TS and mostly WinXP clients. I would hope that I could use Win2008 WITHOUT the Easy Print feature implemented and see no increase in print latency. A 30-45 second delay won't fly with our users. What I'm interested in is whether or not the Easy Print feature will affect print latency. I may not be able to find that out until I get a 2008 pilot box in place.
As for RemoteApp, it does sound like a nice option.
The security benefit you mention would not really help me though. I have a Windows Active Directory Organizational Unit set up that I simply move my Terminal Servers into which locks them down so users can't hurt anything on the TS while logged-in to their remote desktop profiles.
One minor downside I can think of, for me, with regard to moving to TS RemoteApp is that now when a user needs help, it's very easy for me to shadow their terminal session and see their TS desktop. But if they're not actually logging-in to a remote desktop session, we would have to get used to using the Windows 7 (which users will be on by year-end) Windows Remote Assistance feature. This method is not as convenient as simply shadowing their remote deskop session on the TS.
Thanks again. This is a very useful discussion for me.
