My biggest problem with F-Bodies is the demographic of their buyers.
Far too many punk kids, white trash, and urban youth use it to fulfill their horribly undeveloped self-esteems. As such, people mod them to be loud and obnoxious, which often precedes or leads to dangerous highway racing. There is a reason why insurance rates on F-bodies for the 16-28 age group has historically been higher (last 10 years) than mustangs -- the buyer demographic drives them recklessly, which leads to accidents. Most industry insurance figures will provide this picture (at least any national company, like GEICO). The previous comment about the mullet wearing f-body driver is scarily close to the actual reality.
Every time I see 2 more f-bodies racing down the highway at 110 mph, I am reminded of 2 people CLOSE to me where one has a. been injured in a similar situation, in a T/A, and b. the other is now quite honestly a human vegetable (a la Terri Schavo) from driving his SS Camaro on a highway curve at a high speed. The car of course flipped over.
Both drivers were immature youths who, the moment they came into some money, bought the fastest car on the market for the money, and then drove it exactly as the car encourages you to drive it. Dropping that powerful engine into the seriously disadvantaged body/frame/chassis of the modern f-bodies was a mistake by GM; not everyone knows how to handle solid axle ****boxes, RWD, at 110 mph. Especially the youth market that GM specifically targeted.
I am of course generalizing, but that is the point of this post. Insurance rates alone on that age group are enough to support the generalization. Mustangs have, for the last 15 years at least, had a far more diverse ownership demographic, and a lower accident rate.
Did I mention that the build quality on those f-body cars sucks? While Mustangs are no strangers to squeaks and rattles, the years 1997-2004 as reported by Auto MSN, Consumer Reports, and similar publicaations have marked the V6 and GT Mustang an above average car in reliability. I have an older v6 myself (and an 05), and it is going strong at near 100K miles - no unscheduled maintanence has ever been done. In fact, the 2004 Mustang was THE most reliable domestic car last year, virtually tying the Honda Accord v6.
A quick look at CR for 1997-2002 f-body models will verify what every one who doesn't want to own an f-body already knows - reliability is "signfiicantly below average." (I have the CR almanac - used car guide) Piston slap, fuel injection problems, and transmission failures (especially on 97-99 models) are among the most common reported problems, well before 100,000 miles.
CR is not the end all be all, and does suffer from some adverse selection problems in its data pool, but the Mustang is on the same ground, making the comparison on equal footing.
If it seems like I am being hard on the f-body SS or T/A versions, I am. There are far too many problems with that car for it to be a daily driver, or anything but a drag strip racer (perhaps its horrible visibility or overly long front). I will always respect the engineering of the engines (no pun intended), but the cars dissapoint my sense of responsibility.
Just my 2 cents.