I've had many good experiences with ebayers....when I did my research and found out the feedback and emailed the person for a response BEFORE I bought. In general if you order from a power seller or a buisness with a high feedback you will find it a pleasant experience. Many people on ebay frequently check their email but some get backlogged. If they are a good seller you should be able to get a response out of them within 24hrs.
It also helps to do your research on items you want. Look in the online stores like
www.newegg.com first. They are one of the easiest to work with.