How strong are 700cc wheels?

I'm a big lad (a svelte 97kg now, but i've been as heavy as 110kg) and although i've popped spokes and dented a few rims i've never destroyed a 700c wheel out on the road - and that's not for want of opportunity. the couple of times i've done for an mtb wheel on the trails it's always been because the wheel got caught and flipped the bars sideways, putting a huge amount of lateral force on the wheel which it's not really designed to cope with. that's a much less likely scenario on a road bike.

if you're worried at all about the surfaces you're riding on then you can fit a wider tyre: most road bikes come specced with 23mm tyres but i run 25s as a matter of course and don't find them any slower.

generally speaking they will be fine, people use 700C wheels for cyclo-cross and all sorts of other rufty-tufty riding

obviously don't crash through holes and up and down kerbs like you would on your mtb and instead employ a certain amount of 'finesse' and 'common sense'