I think your opinion about this matter depends a lot on why you abstain from the animal products you do. If you're eating vegetarian/vegan for health reasons, obviously you're not going to care about wearing leather or not. And if part of the reason is for environmental reasons...well, I'm not sure what the effect of man-made materials are on the Earth. I would say that from I've read, leather doesn't sound that much better.
What has your experience been with this subject matter?
In upcoming posts I will post about where I buy my vegan shoes, etc. But, for now, I must go, my job calls!