Validity Issuses
The main thing to watch for are visas that start running out from the day they are issued. Although this situation is increasingly rare, it does still occur, so be sure to check beforehand.
Visa application forms often request an entry point and entry date. In our experience, these have been flexible, but we've heard annecdotal stories of people saying they'll be entering on one day, showing up a few days early and being turned away -- this has not been our personal experience though.