Any model in particular?
http://www.amazon.com/Seiko-S141-Sto.../dp/B0002FFBPM
This is the model my coach lent to us to use. Very solid product, but quite expensive for a stopwatch. You get what you pay for, though.
An important thing to note - and not to criticize you in any way - is that a stopwatch is only as good as its operator. In order to not get accurate starts, buttons can be quite sensitive - I.E. the threshold of activation of a button should be low.
So...practice makes perfect. But the stopwatch itself is important as well.