Whatever you do, I recommend first putting down some chemicals to "waterproof" the concrete. Some products are better than others (I like the type that crystalizes, and can thus fill in new cracks if they appear over time) but they all do one thing really well: They cut done on humidity coming through the floor.
Shops have lots of expensive stuff that likes to rust.
As for the surface, IMO a good quality 2-part epoxy paint is all you need. It's much nicer than bare concrete.
- But I mean a GOOD paint. High solids and oil-based. Not that stuff they sell at Home Depot for garages.