mate standard and reasonably modded cosworths are usually very reliable. It is only when we start messing about with the damn things squeezing more and more power out of it that they cause you grief. If I was to run a cosworth for everyday use, I would personally opt for a stage 3 (330bhp) setup, nice and simple and still got some power there if you want to give her a right footing.
If they have been looked after, they treat you very well.