I had the 106, and I currently have the 108 pioneer burners, and I know they work great for ps2, I have not yet tried a dual layer on the 108 yet, because they arent available locally that I have seen and they are fairly expensive. But I do know they work great for ps2, on +r media. I am using them with a I believe v4, or v5 ps2, with a magic 3.1 chip. Just a little help hopefully. The 108 I had gotten for around 65$ on pricewatch.
LG GSA-4120B with A115 firmware and it's been very reliable burner, I've been using it about 6 months now and mostly for PS2 backups. I haven't tried DL yet due to problems finding them from local shops but that situation will change in about 2 weeks when my german gift arrives :D
damn! I just took alook on pricewatch.com and the 109 is now cheaper than the 108 is currently... grrr.. but anyways according to pricewatch, you can grab the 109 for 64.99 after shipping. In either the black or the beige from a place called gogocity.com which also has a rating from pricewatch customers at 4 out of 5 stars. Not bad.
I picked up a pack of dual layer verbatim +r disks today at walmart for like 20$ after tax, and GT4 worked perfectly using tonix dual layer patch then burning. Once again, I am using the 108.. I myself am partial to pioneer seeing as what I have witnessed. Hope it helps. Also, like i said, from pricewatch 65$ shipped.. cant beat that for the 109.