Never been caught myself, and the same as most of the others, never heard of anyone else being caught (at least until now-- good on ya Ric Hardgear, you played it right and didn't let the Gardai intimidate you).
I've only ever had 2 punts in hotels, and those are the only locations where I've had even so much as a slight worry about anyone copping-on to what I was at, but even then not all that worried. Only real worry is getting asked "May I help you, sir"? by the folks at the front desk. As for going into apts, which has been the vast majority of my punting visits, I've had no worries there either, as there's no way anyone else could really know what you're doing. Even if you're seen going in or out by someone else that lives in the building, there's no way for them to really know what you are/were doing there, and most will mind their own business and simply assume you either live there too and they just don't know you, or were thee visiting someone you know.
And as for being caught 'red-handed' by the Gardai, I'd say it's highly unlikely, short of you being in with a lady in the middle of a bust/raid! What can they possibly say or do to you, if they saw you on your way in or out of an appointment? The only thing they could really say is "have a good punt" or ask you "how was it?" afterward! As has been discussed at length on the site, punting under certain conditions is perfectly legal, and it's this that I keep in mind when I go punting!