It is always worth researching feedback whether you are buying or selling. Feedback is a two way process though, so always be prepared to spend a few moments following the feedback trail.
If someone has a good record of positive feedback it's always worth reading some of the comments:
Sellers - Do people mention speed in getting the goods to them? Is good packaging mentioned? Good comms? Friendly? Check the detailed feedback number eBay introduced recently and see what they tell you about a seller.
Buyers - Speedy payer? Good comms? Friendly?
If you see a lot of these sort of comments, then you are almost certainly going to do well if you trade with them, and remember that we all have to start somewhere, so just because someone is new doesn't mean you should avoid them. If you look in the top right corner of the feedback page it will tell you how long someone has been on eBay, so you can judge the amount of feedback against how long they have been trading. Someone who has achieved high feedback numbers in a very short space of time could be a very successful business new to eBay, but it could also indicate a scammer with false feedback.
Multiple feedback from individuals may not be a bad thing as it is not unusual for people to buy/sell 8 or 10 things in one purchase. If you see this just consider it against the total feedback they have, and, if you can follow the feedback trail as described below. There are cases of people creating dummy items that they "sell" to freinds/family and give each other feedback to boost their rating, but you can usually spot these if you follow the advice here and check further. A lot of items that have apparently sold for 0.01p would give me cause for concern.
Where someone has had a negative or neutral comment, click on the feedback for the person who gave that feedback and see what sort of a person they are. Sometimes you will find they themselves have a few negatives and neutrals so you can make your own mind up about the issue. People do leave bad feedback as revenge unfortunately, rather than as a legitimate comment on the transaction.
If the poor feedback is recent the transaction might still be available; if the item number has a blue line under it, click on that link and see what it was that the bad feedback referred to. Is it something like the item you want buy from/sell to this person? Either way it can help you make up your mind.
If buying, look at the item description. Some sellers put small print in, and you might find something like "I will leave feedback once I receive yours". Personally I try to avoid people like this as I wonder what their motive is. If I sell to someone I leave feedback as soon as I receive payment. If I buy I leave it as soon as I get the item. That to me is what feedback is all about.
The other thing I do when looking at people's feedback is to click on the tab that says "Left for others". It amazes me how many times I come across someone who has never left feedback for anyone else, despite the fact that their own feedback is often well into three figures.
The other side of that coin, especially for new people on eBay, is how often sellers won't leave them feedback - I've had a number of bids where the feedback is less than 5 say, but when you look at their record they've actually left 10+ for others, so their feedback number is low only because of lazy people, and some of the worst are those with huge feedback numbers.
The other thing you get from checking what feedback people have left for others is you can see the tone of it; do they use abusive terms? If so do you want to deal with someone like that? It's up to you, but I wouldn't.
eBay is a great place to buy and sell things, and one of the things that makes it great is the transparency that you get from having feedback. Taking a little time to check people out is always worth it and, if you're unsure about dealing with someone, try using the Question facility and see what response you get. The way they treat your enquiry can tell you a lot. If you're still in doubt then walk away.
If something goes wrong in a transaction, always try and resolve it through correspondence before leaving negative or neutral feedback. We all make mistakes from time to time, and a good seller will always be happy to rectify a problem to keep the customer happy. Anything other than positive feedback should be the last resort, but do use it when appropriate so that others can be aware.
Have fun, and please do leave feedback (including a yes or no vote for this review). If you buy from, or sell to, me you can be sure I'll leave it for you, usually on the same day that you pay me.