A little bit of Vaseline is VERY bad for a flute- it will eventually form a film on the pads and cause really premature wear.
I suspect that some of these 'Customer Comments' with glowing praise and talk about buying the flutes for students are actually 1)a good friend of the seller or 2)the seller himself, with a different email address.
The reason that I suspect this is because the other feedback does not match- the dissatisfied customers are NOT easily given money back or a different flute without problems.
I second Patrick's most excellent advice: do not buy a flute on eBay from someone with that kind of feedback
From what I've seen, the Power Sellers seem to be the absolute worst ones for response to negative feedback- they flip out! (Instead of trying to solve your problem.)
For a good used Yamaha student model, try Kara (a poster here) or Nancy Shinn of www.flutestar.com . Either of these gals will sell you a quality Yamaha for a very good price, and it will be overhauled to play really well. Best of all, you aren't likely to have problems- but these gals will try to solve them if they do happen.
<Added>By the way, the feedback on eBay is really only supposed to do with paying your money and getting the product described in the auction in a timely and professional manner. Feedback also gives us a glimpse of what happens with a specific seller when a problem arises.
My opinion is that most people buying these flutes send their feedback in right away after recieving (promptly) the very same flute pictured and described in the auction. They usually have NOT taken it to a flute teacher, or tried to play it themselves. It is usually a few days or weeks too late when the buyer cottons on to the fact that this is a cheap toy- not a real flute.
Good job looking at the feedback from dissatisfied customers- there's your answer.