Over the years I've read all manner of comments about epoxy floor coatings. Almost every comment has been contradicted somewhere or other. It makes it tough to know what is "best". That being said, here's my personal experience.
About 8 years ago I did a garage expansion. Once the concrete floor "cured", about 3 months, I decided to give the floor a coating. I looked at several, but then figured that the Rust o leum kit available at most hardware stores was worth a shot. As mentioned above prep is everything, just like any other coating procedure. I followed the intructions to a T, even called their tech line because the instructions didn't say anything about etching the surface. They were adamant to NOT etch the surface, just use the cleaning solution they provided (wouldn't confirm if it did a micro etch, but it seems plausible). It took two kits to do the amount of floor I had, cost at the time was under $100. Over the years it's endured oil, grease, solvent, paint overspray, weld splatter, grinding sparks, jack stands, metal wheels, and all the other "normal" whacked out car guy things. Also as mentioned above, I am careful about how I drag things across the floor, but not overly so. So far not a glitch. No lifts, tears, apparent wear, or serious stains. I don't know how any other surface finish could have done any more for me. The thing I like best is how it makes cleanup easier.
The probable advantages I had were that the concrete was unused (except for drywall debris) so therefore easy to prep/clean. May or may not have been as satisfactory over oil stains, I just don't know. I do have a vapor barrier under the slab. The slab has been very stable and has no cracks. Can't speak to gravel in the tires other than sand size particles, no problem from that, though admittedly this is more of a building/storing area than a traffic way. So called "hot tires" haven't been an issue, but again, that's not a daily occurrance. For a serious hobbyist application it's been great. In a commercial application I might step up to the more expensive professionally applied system, but a home shop just doesn't warrant that.
The picture below is shortly after move in, it's nowhere near as neat or open as that anymore!
