Here are links to buy a 105 and then a 106. They are listed the same speeds for each media type, except the one I've linked says the 106 will do 2.4X on a dvd-r rw rewrite.
http://www.pricegrabber.com/search_getprod.php/masterid=659072/mode=google1/ut=40dba31e022d50b8
http://www.pricegrabber.com/search_...932493/search=pioneer 106/ut=40dba31e022d50b8
Prices vary from dealer to dealer across the "net". The cheapest 105 I found was for $149, the most expensive was $299! ---(probably external)
The dimensions actually change from site to site, but most agree on about 7.8 inches (198mm) long (deep). peterp100 said that the older drives are bigger, but I have not found any sites that list any more than a .1 inch or a few millimeters difference. It's possible that he was using the old 103 (OH THOSE WERE THE DAYS~!
http://www.macrumors.com/pages/2002/01/20020124194805.shtml )
In contrast, the dvd player in my g4 (hitatchi gd-7000) --came with mac-- is only 7.1 inches. There is an aluminum cover over the back which attaches to the mounting, but it can be removed and there is at least 2 inches until it hits the power supply. It seems to me (ISTM) that Apple put the cover there for cosmetic reasons only.
I wish I could post a direct link from xlr8yourmac.com's database, but it looks like each search produces a temp file, and cannot be linked to. (For sanity's sake, I won't copy/paste). Basically the database is a bunch of postings that people leave when they have gotten a 106 and tried to install. In 91.2% of the cases

, users have installed hacked drivers just to get burn capabilities. This requires either terminal use or booting to OS9 to replace manually--not really a problem, but-- Once they've done that, many times the stupid thing still doesn't work with iDVD (the whole point of me starting this thread).
This can be attributed to driver drivers, system config, and in at least one case, the ATI graphics drivers!
Arden, you are right that the 105 is the way to go right now, because of the shear crap involved in making the 106 work. BUT the 106 is supposedly going to be supported in panther, and it definitely is the better drive. At this point I am going to wait until panther is out to make any decisions. (People have posted in the database that it barely works under jag, but works like a snap in panther betas). If the 105 was only $100, I would jump on it. But its price is really just as variable as the 106, anywhere from $150-$300.
The 106 is apparently THE dvd writer out right now, price to performance, so it would be nice if Apple did accept it to replace the A05/105 series.Of course it may be a coincidence and glitch in Panther and not work when 10.3 comes out.
Not to mention the plextor 708, which comes out within the month (8x writer).
http://www.cdfreaks.com/news/7487
I'd like to thank xlr8yourmac and google for my research on this thesis.