Looks like I'm almost alone in this (or others are keeping quiet for fear of being judged) but yes, we do it. If we stay in a hotel we occasionally use the baby listening service and eat as a couple in the hotel restaurant. Only once outside the UK, but in several places in the UK. My parents did it when we were kids, so maybe that's why I think it's OK. I do understand people's concerns - DH did need a bit of persuading the first time we did it - but on balance we choose to do it occasionally.
Most evenings, we do eat with the kids, but it means eating early (or having grumpy kids) and then creeping round so as not to wake them for the rest of the evening. As they get older, we do it less as they are more capable of staying up later. But it's nice to have an alternative.
For those suggesting "but what if they get sick?", it's not much different to being at home. If they are ill but not making a noise then we could easily not notice for a couple of hours at home - we don't go and check on them every 10 minutes. If they are crying /or coughing or generally making a noise then the baby listening person will hear and call for us.
It probably helps that our kids (9 and 7) have between them only ever got out of bed during the evening (once settled) about half a dozen times in their whole lives. If there's a problem they call for us (which can be annoying when they could get themselves a tissue / teddy / pair of socks, but is reassuring when in a hotel).
Yes, of course there is a small risk of abduction. And the Madeleine abduction did make us stop and think. We ask for a non-ground floor room which reduces the risk, and as a PP pointed out, is someone really likely to try round all the rooms in the hope of finding a child left alone? And quite frankly it could happen elsewhere if I had a momentary lapse of concentration eg in the park or the shops, but doesn't stop us doing that. Or someone could break into our house.
Those who are saying "but aren't holidays about being with the kids" well yes they are, and they are the only time that we spend more than a weekend as a whole family. But on a two week holiday, having maybe three meals of two hours max as a couple doesn't seem excessive.
Yes, we could self cater and often do - but as the main cook / cleaner / organiser at home, a few days in a hotel is more relaxing for me.