there is a lot to look for in a dvd-rom...Since many are using it as their sole cd reader for the system it needs to be a good cd data reader as well.
1)cd data reading (how close to their claims!!!)
2)dae ripping (so you can burn audio cd's on the fly at your cd-rws max)
3)cd access times
4)dvd data reading
5)dvd ripping (backing up dvds to harddrive or to future dvd-rw
6)dvd access times
also:
7)compatability to different cd media as well as future dvd-rw media...
good review site to look at is
www.storagereview.com
edit: forgot 8)noise factor
go Pioneer/aopen 106/116 first then toshiba...read review sited above.