I can speak for six Plextor PX-712A drives. I just took two out of my system (TLA#0101 on the drive - not TLA#0000 as stated elsewhere on this forum, manufactured in May 2004) - and sold them to a friend. I'd been using these for about a year, with no problems. These drives made no unexpected noise when ejecting or retracting the tray.
I also bought four more PX-712A/T3B drives this month (they were going cheap, and they were black - which goes very nicely with the Antec P160 cases I use!) These were all TLA#0105, manufactured in September 2004. All but one of these drives make a similar noise - but the ones that make noise vary from drive to drive. One drive is very quiet, but you can hear the noise when you insert a disc. The other two drives make a slightly louder noise, but nothing worrisome. Certainly nothing I'd have noticed if I hadn't read this thread beforehand - and listening to the noise, it reminded me of a standalone DVD player that made the same noise when the tray was being pulled in. The act of pulling the tray doesn't seem to move the disc in any way - if ejected as soon as the tray is fully retracted, the disc stays in the same position.
The noise doesn't seem to have any bearing on reliability - indeed, the only drive that didn't make any noise has proven to be faulty after just one day of testing - ~450 PIE errors in the middle of several discs (on the same batch of 8x DVD+R Taiyo Yuden media used to test all other five drives) convinced me that it was worth returning the drive. I have tested three other drives so far, and I'll test the remaining two tonight (I suspect they will do quite well; writing and verifying a 4363MB disc took 12 minutes and 50 seconds on each drive, with the final read speed being 11.7x). Only one of the three others approached 90 for PIE in the worst case, and the other two stayed well below 30 - even at the end of a disc. I'm quite happy with these results. All drives tested returned 0 POF, and all burns were performed at 12x.