Tough question. I'd say "that depends" on several factors.
MOST of the time, a slow connection is just fine. We had customers on satalite connections making this work. I don't recommend that.
MOST of the time, you're only sending XML files over that connection.
SOME of the time, you're synchronizing new packages. If the packages are HUGE, you either need a fast connection OR a lot of advanced planning.
ONE time, you synchronize everything (unless you prestage) and that can take a while.
IF you are deploying images in that location, those are HUGE packages, and uh - can take time to replicate out. IF the systems are sent back to be re-imaged, then don't put task out there, just package, and you'll be fine.
So, some thoughts.