As far as I can tell from the trade rags high reliability makes it pretty far down the food chain, if only because it’s cost effective – it costs too much to honor warranty if the machines are crap.
The only recent major brand I’ve seen that was downright shoddy was the first few years of eMachines, the insides of which look like the junk you’d find in a furby. I think they even bumped up their game a bit from their first offerings but not that far.
These days if you bought the cheapest machine at Walmart then you’d probably be stuck with junk, but any known major brand [Dell, Gateway, ASUS, Acer, Lenovo, HP (not counting the cheapest HP, they are junk) ...] I think you could power-cycle those thousands of times before that caused a problem.
Basically I wouldn’t worry about power-cycling a typical consumer-grade computer twice daily (morning session / evening session). Your mileage can vary.