K7S5A (SiS 735) rev 1: not many, one dead after almost two years, repalced w/ L7S7A2.
K7S5A (SiS 735) rev 3: several, all fine.
K7S5A (SiS 735) Pro: several, all fine.
L7S7A2 (SiS 746): Two fine, one recently RMA'd, board recieved from RMA is fine.
Total of 32 ECS SiS boards used now (30 from Newegg), and while I eventually lost track of the specific K7S5As, there have now been...
1 death, after over 23 months of use in a very hot, closed, dusty space.
4 batteries that needed replacing.
1 bad board.
As long as you spend the extra few bucks for some decent RAM (Kingston ValueRAM or basic Crucial, FI) and a decent PSU ($30-$35 300w Forton, Enlight, Enhance, etc.), there will be almost no problems (after 30 boards, you find some problems. Period. No matter what board it is).
You get better as you pay more, like some of the NForce2 boards (I love the 8RDA+), but if you're on a tight budget, I'd recommend ECS SiS boards.