Bump, as I have a similar question.
Unsure of what disk read speed one should look for. $50 gets a 4X BD-ROM drive, but I guess (reading reviews on Newegg) that this can result in stuttering? For $10 more, you get 10X speed, and $20 gets 12X (but only a 2MB cache, as opposed to the $60 models' 4MB cache -- is this important?) Then, the $70-$100 range seems to be all 8X drives... it's confusing, to say the least.
Additionally, am I correct in understanding that you also need to buy special software to play BD-ROM movies? And how much does that software set one back?