The problems I've had with Presta valves are very limited. One is that my old floor pump is nearly 30 years old and the pump head is so worn it pops off at 80 psi. I solved that with a new pump which screws onto the valve, which brings me to my second problem, which is that the valve cores on Vittoria tubes sometimes aren't screwed down tight and instead of the pump head unscrewing from the valve, the valve core itself unscrews and all the air I just pumped in blows out rather dramatically. It's a mild annoyance in the garage before a ride, but on the road I use a LeZyne minipump which also threads onto the valve and it takes a lot longer to get a tire up to useful pressure with a minipump, and if I have to do that TWICE, it's real damn annoying.