Okay, I did Denver, CO to Seattle, WA, to Boston, MA (and back after I broke the darn thing in Ohio and got it reparied in MA [didn't know anything about wrenchin' then]).
At certain speeds, it of course vibrated like Hell. That will hurt your hands AND feet after about 1000 miles (in a day... yes, I did that too; Denver (actually FT. Collins, an hour north of Denver) to Mt Rushmore & back in 22 hours). When you're riding on the freeway, and you really feel the vibrations, change your speed just a little and it will help a lot...
a real lot.
The bikw can handle it... I punished, punished, punished my savage on that long trip. It was about 5000 miles in about 5 days of riding time. It "broke down" with about 800 miles to go. However,
it kept going! It jsut wouldn't go over 65 mph, even down hill... The cam chain tensioner broke, but it wouldn't die. Additionally, keep an eye on your oil (of course!).
Seat: bleh! I had highway bars on it, which really helped as I could move around on it quite a bit. If you put the pass. foot pegs down, you can safely put your feet on there and ride it like a sport bike. You can also sit on the "hump," where the driver and pass seat meet, which is surprisngly comfortable. Also, with the pass. pegs down, you can sit on the pass. seat and put your feet on the pass pegs... not recomended for turns... or without a sissy bar.
Good luck!