Plenty of slabs are cracked, spalled, chipped, dirty and in just generally crappy shape, but those are all good reasons TO coat with epoxy!
If the floor is in bad condition it's a great candidate for a resin system as long as it doesn't have major moisture problems also. Run a quick and simple test to see if your floor has problems... Lay down 2' x 2' pieces of seamless plastic on a few spots around the floor and tape down the edges with duct tape. After a few days remove the tape and check for moisture or condensation on the floor or the bottom of the plastic. If you see moisture you may have a problem with hydrostatic pressure, so consult with a coating pro, or give us a call. If there's no moisture you're probably good to coat.
Keep in mind that even if you have hydrostatic water pressure a quality coating system can handle it if the pressure isn't too high.
As far as the other issues associated with a old and abused floor most all of those problems can be handled. Here's a floor that looked like it was beyond help, but a little TLC and some quality products was all it really needed.