Completely objectively? I'll go step by step...
Steering. These are street-legalized race bikes, they turn into corners HARD, almost like "Hey I just thought I wanted to turn left and I'm going left now.". I know it sounds preposterous but it really is that quick on a lot of supersports. They're not designed to forgive mistakes either. They're designed to be able to ride to the track, turn out a hot lap, and ride back home.
Engines. These are 0.6L inline 4 engines producing around 120 HP. to put that into perspective, a Corvette ZR-1 (supercharged 6.2L V8) produces 638 HP. If the 600's engine were increased to the size of the Corvette's, and the same power to size ratio was used, we'd be looking at a 6.2L V8 that pushes 1,240 HP BEFORE adding a supercharger to the mix.
Power to weight ratio. The Corvette ZR-1 also has a power to weight ratio of 5.4 lbs for every horsepower, which by any car's standards is AMAZING. In contrast though, the 2011 GSX-R600 has a power to weight ratio of 3.5 pounds for every horsepower. Ask any kind of racer and most will tell you they'd kill without a second thought for that kind of power to weight increase.
Weight. The 2011 GSX-R600 is claiming a dry weight of 419 lbs, which is very light for a bike (especially compared to the Fat Bob you've ridden). The key difference there is where the weight is located. Sportbike designers have been working for well over two decades to get the mass centralized and high in the frame, which aids lean-in when cornering. As a result, your average sportbike is much heavier feeling than your average cruiser, which tend to have very low centers of gravity. The higher COG also makes it a lot less stable at low speeds and makes it very quick to go over (firsthand experience on them trying to go over, trust me on this one.)
Now for the subjective parts...
Comfort. In a phrase, not much. Like I said earlier, these bikes are designed to be ridden on the track, not over the river and through the woods to Grandmother's house. They're not comfortable, you're laying on the tank, your legs are scrunched up under you, your neck will get sore, your wrists will get sore, it's just not comfortable. The next time you're out driving around take a good look at the sportbike riders you see riding around. Notice how almost every one of them will put their left hand on their hip when they get up to cruising speed. That's because they can use the support for their back and wrists. To put the neck strain in perspective, put on a helmet, lay on your bed on your stomach, and try reading a book for 20 minutes without resting your head on a pillow or anything.
Control. Can you handle it? Possibly, I can't tell you what you can and can't handle. I can however tell you what I've seen happen to a lot of inexperienced riders (including myself.) While driving around have you ever accidentally revved up your engine a little high to take off? Have you ever accidentally dropped the clutch? Ever accidentally done a small burnout? With a sportbike you don't have the advantage of weight and tire slip. A little extra throttle and a little extra-fast release of the clutch sends the nose skyward. Trust me I've done it. One second you're taking off from a light normally, the next the front tire suddenly feels REALLY light and you're wondering why you're looking at the streetlights instead of at the road in front of you.
Now... that's my objective and subjective opinion of the matter at hand. Maybe you'll listen, maybe you won't. But either way the facts are the facts, and the opinions are mine!
Have owned - 2001 Suzuki Volusia
Current bike - 2005 Kawasaki Z750S
MMI Graduation date January 9th, 2009. Factory Certifications in Suzuki and Yamaha