As with most others here, I go OEM whenever possible. Savings are usually in the 10% range, and you don't get the large, fancy box. Drivers are almost always supplied with both retail and OEM versions, and are almost always out-of-date for both. I haven't used a supplied driver disk for years.
Warranty is the only sticking point. OEM warranties are usually good only through the store where they were purchased, and are typically 30 days. The retail warranty is good through the manufacturer, and is a period of years, not days. That said, I prefer the OEM warranty. Just take it back to where you purchased it, and the good stores will replace it then and there. Sending retail packaged parts back for warranty replacement is a long process. Plus, for things like video cards, I find they either work or they don't. Unless you overclock them to death, they'll probably still be working a hundred years from now. You won't be.
Besides, OEM is environmentally-friendly
Regards,
Craig