I like the SureThing software the best, it's really easy and faster than most I've tried. I believe they also did the Sonic software mentioned in the OP.
The speed of doing a LightScribe label isn't based on the software, but on LightScribe drives themselves. They just need time to burn the image onto the disc. Whatever software you use won't make a difference.
For quickest results, use circular text (SureThing does this nicely) and no graphics. LightScribe burns the label in rings on the disc (just like the data), so the more rings the text touches the more work it has to do. Regular text touches lots of rings and 14 lines might touch almost all of them. But circular text can say the same thing while only touching a few.
It's still relatively slow, but the LightScribe discs can look pretty cool and there's no label to mess with.
Hope this helps!