I 've bought my px-708a oct2003 (250Eur). I had these problems:
1) The first nero version (latest at oct2k3) that i used was 126.96.36.199. I threw away 3 plextor +R discs of 3Euros each. I started using -R media! After 2-3 days 188.8.131.52 was released, so proplem solved
2) My first 8x burns were low quality, cause ricoh 4x (R01-02) and TY 4x aren't the ideal media for burning at 8x. So i used 4x instead. Problem solved.
3) My cd-rec was a 20x ricoh mp7200, so 40x was an improvement. I burned over 100 smartbuy (prodisk) cd's. One day, i' ve put an old TDK 4x cd-rw. Drive could't erase it. Suddenly, smartbuys couldn't burn anymore. I used TYgold prof, and they worked. After some days they didn't. It couldn't read nothing says CD. Problem exists.
Conclusions: I use the drive for DVD burning (that's why i bought it), and with 8x certified media it works fine. I've tried ritek 8x (ricoh r02-03). But this media is expensive (2Eur bulk). So i use bulk TY that costs me 1.3Eur. But i still burn at 4x. After six+ months of burning, i think that plextor disappointed me. I never had so many problems with a pc part. I don't say it's not a good drive. It burns DVD fine (small error rates etc., especially TY). But it's not what i expected from the money and the brand. I 've seen many drives (liteon 811s, 411s, sony dru510a and more), and only mine had so many problems. Worst is that if i use warranty i'll stay without dvd burner about 15-30 days.