It's OK to have 'concerns' but what concerns do you have? Did you once own a home on a concrete slab before that had problems? Do you know someone else that has/had 'problems' with such construction?
If you have no real 'cause' for concern, and the answer to the 2 questions I posed are NO and NO, then it's time for a Home Inspection. Find an ASHI-Approved Home Inspector, or the like. AT least find one with the type of qualifications that an ASHI one has. DON'T use a Home Inspector that's recommended by the Realtor or Home Owners. There could be some 'bias' there. Find one on your own, or preferably find one that's recommended by friends or family. If you can find an Inspector that's kind of operates outside your area (so to speak), chances are good he won't know your Realtor or hasn't done business w/them before. (You'd be surprised how many Inspectors are in the 'pockets' of the Realtors!) So do be aware.
The only 'thing' I don't personally like about a home on a slab is the plumbing and wiring 'issues'. If you have plumbing 'inside/under' the concrete (or the same w/your wiring), and if there's a problem, well ..., you have BIGGER problems than if the home was built over a basement or a crawlspace or the like. There may be a need to bust-up the concrete to fix any problems. Again, this is where you might want to 'interview' your probable Home Inspector and find out if he's done a few of them. If not, move on.
Other than that, I'd say they're fine. Others may have more to say so don't go away too soon. Stick around for more feedback (I hope.) My best to ya and hope this helps.