Well, I've had a few NEC and Pioneer drives, and voted for the NEC here. First, I had an NEC 1300, which was pretty good, but occasionally a little picky with -R media. Good burner on the whole, and discs tended to be very compatible in standalones.
Then had a Pioneer 106, which was a great drive. Pretty much no coasters, and build quality felt better than the NEC. Burnt probably about 200 DVDs on it in total, and it's still working fine. Burns were better than the NEC 1300.
Now have an NEC 2510, and it's simply fantastic. Burns are extremely nice. Have had no problems on any media I've thrown at it, NEC seem to be ok (if a little slow - still no Ritek +DL) with firmware updates. Definitely the best drive I've had so far, though it is a little slow for an 8x drive. And the greatest thing is that it's also cheaper than the less good drives (Sony/Liteon, etc..).
A no-brainer for me, though you'd prob also be very happy with the Pioneer. If you can wait, then wait for drives that do -DL, and maybe 8x +/-RW?