It's a good bike. 77k is not that much on a bike like that. Many people will easily take theirs over 150k with no major issues.
That price is fair for one that has been well taken care of and a good price if it comes with useful upgrades like aftermarket seat, crash bars, skid plate and more. Who makes the hard case luggage?
Ask if the stator has been replaced. Until about 1yr ago, the older stators they used had a design flaw that made them prone to overheating and failing over time. The new stators that Suzuki provides have fixed this flaw, but they don't offer it as a recall item -> pre-2012 bikes have to pay for it out of pocket. Suspension might be due for some love as well as steering head bearings and valves.
Asides from that, and with any bike, if it received regular maintenance, the bike should be fine. Mine has just under 150k on it and is still running quite well.
edit: also check out
www.Stromtroopers.com if you haven't for tons of info about these bikes.