I only burn single layer 4.7gb DVD+R discs as "data discs"
Typically filled with mp3 files for playback in my Sony MEX-DV2200 car Stereo.
It typically takes ~8minutes to burn and verify a 98% full disc
I use Roxio 2010 to do my burning on my Q9450 quad-core computer running Windows 7 Pro 64bit.
My Burner is a Sony-Optiarc AD-7261S
One of these days I'll buy a spindle pack of DL discs as my head unit will play DL data discs, but as things stand I can "tolerate" a single layer mix disc for about six weeks before I switch to another disc...