Is there a way to see how fast a WL book is moving through the system?  I have 3 books I really want right now.  They will be for my keeper shelf if they meet my conditions.  One I am in first position for.  One I am #5 of 6, and the other I am #12 of 12.  I can buy all 3 off ebay for around $21.  Just debating if I should wait or buy.

not really....you can check back and see if you move up very quickly or not.

and it all comes down to how much you want the books now vs. waiting.  I have close to 400 books on my TBR pile so I can afford to wait until I whittle this pile down

There is no official way to find out.  I check back from time to time to see my standing.  If I am moving up... the way I guess that is seeing how many people are behind me now.  If I see folks stacking up behind me and my number getting closer to the top, I consider it "moving".  However, there are some where I have been 1 or 1 or 3 of 3 for months now... and it seems those books just don't come up often.  However, the books that have large waiting lists, tend to move faster.   Those are my thoughts.. not really an answer though.