No really, the bike is very nice.  The motor is one of the sweetest ever put to a machine.  In my experience, which is limited, there are a few motors that are real stand outs.  The first one that always springs to mind is the SV650/Vstrom motor.  Another is the TMax.  Finally and maybe the best is the Bonneville motor.  None of these are the fastest or most powerful bikes, even in their class, but they are so pleasant I just smile when I roll the throttle.  Part of it may be the fueling, the way the power is distributed.  Unlike my old Nighthawk, which was soft in low revs or my Ninja which is very twitchy no matter where you are in the rev range, the Bonneville motor is a happy little torque machine.  When rolled hard from a stop you feel like you are on a locomotive as the bike pulls you along.  I bounced off the rev limiter two or three times because I didn't get the sensation from the motor that it was ready to quit.  While my Ninja motor is similar it doesn't have the smooth fueling the Bonnie has.
Another nice surprise for me was the comfort.  I've rented the Bonneville SE in the past and I don't remember it being as comfortable on an all day ride.  I'm even more surprised because this is my first ride since I put my bike away last year.  So putting on a 300+ mile day with little discomfort is a pretty big deal.  I had some foot numbness and neck aches but that was about it.
The handling was nice too but not great.  Compared to the Bonneville SE the bike feels sluggish and a bit heavy in tight turns.  The T100 has a larger front tire and spoked wheels which don't compare well with the SE model in the handling department.  I was surprised how different it was.  That's not to say the bike isn't fun to ride on technical roads, it is, it's just not as good as the other Bonnie.
The bike I had rented tended to backfire quite a bit.  I doubt this is a characteristic of the bike and has more to do with the maintenance from the rental company.  However another tendency did bother me, especially in the beginning was that the clutch didn't engage until you almost fully released the lever.  Very annoying, don't know if that is by design or if it can be corrected with an adjustment.  Finally, I didn't care for the long kickstand that leaned the bike way over when parked.  You really feel the weight of the bike when you pull it off the stand to start it. And since the paragraph seems to all be complaints I should add that I don't care for the manual idle adjustment, I've never seen that before on a fuel injected bike.
The T100 is very stable on the expressway.  I was on a stock bike so there was no windscreen or even a flyscreen.  I think I reached speeds of 85-90 mph at times and I never felt as if the bike was out of control or hard to handle at higher rates of speed. Even on California's grooved interstate pavement.  This is a plus for me because I have been on bikes where freeway speeds weren't comfortable.
To the surprise of the Eagle Rider staff (where I rented the bike) I was getting over 50 mpg on the T100.  Most of my riding was below 55 mph so it's not too amazing a feat however I was working the gears pretty good as there was hardly a straight road for the most part.
I love the look of Bonnies but for me, the SE model is nicer looking.  I know the spoke rims, flat seat and pea-shooter exhaust have a cool retro look but I think the SE with the alloy wheels and megaphone exhausts looks quite a bit better.  Same motor though, so choose the one that makes your heart beat faster.
Neat bike, I really like the Bonneville and if I had the money and space for a fleet of bikes there would be no doubt, I would have one in my garage.
,a beauty!!!!!!