I've had pretty good success with the three Pioneer burners I've had over the years, but I do very little burning anymore now that hard drives are so inexpensive. Each of the Pioneers started to have write problems after about 1,000 burns which is acceptable, but the failure rate of the DVDs was worse. Most of the failures were on the DVD-RWs, so I would stay away from those. The key to good burning and long term reliability is good media. http://www.dvdrhelp.com
is a good resource for drives and media, with a lot of user reviews. You'll see links on the left for DVD Burners and DVD Media.
Right now I am using an external Lite-On Ez-Dub (USB 2.0). For the little burning I do it gets the job done, and I can use it on any system in the house. I think I paid $75 for it. You should be paying about $30-40 for a run of the mill internal drive (Sony, NEC, Lite-On), or about $70-80 if you want a Plextor.
Regarding the dual layer, at $1.50 per disc (over 15c per gig), they are still almost the same cost per gig as hard drives so they are really not worthwhile in my opinion. 5-6 times the cost of single layer for only double the storage. Of the 4000+ DVDs I've burned over the years, I think about 5 were dual layers.