I've had more problems with sellers not on ebay than sellers from ebay , but one person's experience in one person's experience.
What I don't understand is all the griping about ebay. Please name for me an auction house that takes less than a 30% cut and doesn't have a buyer's fee. Ebay is well below 20. Sales tax is a gubmint thing, not an ebay thing, can't blame them for death and taxes.
As for asking questions, if they are relevant, objective, not ambiguous and most importantly, to the point, then yes, you should get an answer. But if you go on and on about your passion for a brand but this one is SL tubing and you want to know the ride characteristics compared to SLX tubing then it would take all my being to ignore you even though I would want to tell you to go **** yourself.
A transaction should easy when kept objective. Whining over the meaning of "excellent" condition is a hell you deserve. Knowing the size and nature of a defect is required.