Of course it's much more fun to travel without having to work.  But the opportunities are more limited.  After my first stint in Korea, I took a trip to Taipei and Bali.  The airfare to Taiwan ended up being free because it was cheaper for my company if I flied Seoul -> Taipei -> Chicago than Seoul -> Chicago.  Then, the trip to Bali was $600 with airfare and hotel and what not.  My guess, if I had done this from the states, it would be at least $2000.
Also, being based in a foreign land allows me to take small trips that I would never consider.  I doubt I ever would have gone to Taiwan on my own, and I 
Definately would not have gone to some of the smaller cities like Kenting or Hualien.
As you said, the downside is not having a home and being far from friends and family.  It's annoying, but I make new friends at each location, and I still keep in touch with old ones (and of course I visit when I swing through the home office).
Not having a home, well, I only graduated college 3 years ago, and in that time I never really 
had a home... just places I'd live in for a year or two.  So that's no loss for me.
That having been said, I should get my ass back to work...
 Evanescence -- Fallen -- My Last Breath
/* random quote */
"Forever shall the wolf in me
 Desire the sheep in you"
 	-Nightwish "Beauty & the Beast"