OK, first off, I appreciate the fact you are looking for more what people do not like about a camera versus what they like. Its easy to follow praise, but a true sign of research to go head first into the negatives.
Pentax, Olympus, Konica Minolta. Right now those are three companies diving into Digital SLRS. The construction of the bodies, designs, are for all purposes the first run (lee-way on the Olympus designs, but lets face facts, E1 not like an E10-E20 design, and E-300 certainly not the E1) of a digital camera and mistakes are there to fix.
Those aforementioned bodies feel awkward and accessories and lenses are hard to come by at a reasonable rate and availability. Some cases can be made for them whether it be the 4/3 sensor on the olympus of the Anti Shake on the Maxxum digital SLR,.... Pentax i have found no good for.
Here is some $0.02 of praise, ridicule, perhaps my opinion. 1: I don't want a sensor that moves (Konica Minolta), and 4/3 system, I am not pumping out 8x10's nor do I care to and quite frankly, never warmed up to the Olympus digital SLR (not saying its a bad camera system, others have used them and love them.... just.... not me.... then again, never really gave them a chance, love my S2)
Look into Canon, Nikon, Fuji..... if you have the bling bling, heck Kodak DCS Pro (Nikon only, the Canon is really bad.... and honestly....this camera is a studio only camera, use it for nothing else, hence, grey area).
Each camera we can make cases for, but the Digital Rebel, 20d, 1d/1ds Mark II's, D70, D2h, D2x, and S2/S3 are all fine digital SLR cameras. Made from companies in it since the beginning and have a solid construction and have things out there to play with.
Full frame versus non full frame, well one hand no focal magnification, but that doesn't mean the sensors are better. From a nikon stance its the fact there sensors don't slightly blur out in the full frame realm, of course canon isn't going to say there does or does not. Its a push pull, fact is, aspect ratio is there of 35mm and quality can be found on both.
To not go overboard and not sell yourself short, I would suggest you look into either the Canon 20D, Nikon D70, or the Fuji S2/S3 depending on money you are looking to spend. I favor Canon glass (L series 2.8 with IS, can't go wrong) over the Nikon VR but both are good and lets not forget the dark horse in the running the Tamron DI series.
It comes down to what feels right with you and you alone. Then look at what you can spend overall and factor lenses, flash's, work within your budget. There will always be something better our there for you in a few months to a year, but it matters is you want the camera now, whats there and does it work for you.
Anything I can do to confuse you further, lemme know
Glorified Unique Photo Counterboy