I was a regular on eBay when the site started to become popular. Back then, it was like a virtual flea market with bargains to be made left and right.
Today it is mostly controlled by businesses and while you will still find auctions by regular people on the site, it is much harder to find bargains now.
The main reason for that in my opinion is that businesses throw their stuff on the market in great numbers which makes it difficult to find "real" auctions on the site.
Whenever I browse eBay I tend to use two browser windows for that. One to display search results or categories, the other to display the item pages.
Using only one browser tab to navigate both takes a lot of time and while eBay's result pages list some information such as price, title and a picture, it fails to display others such as the item's description or seller information.
The Firefox add-on eBay Fusion offers another option which may improve how you use the marketplace significantly. It has been designed by the same author who created Craigslist Fusion, a similar extension for Firefox.
Once you have installed the add-on in Firefox and restarted the browser, you will notice that some eBay tabs will get cut in half automatically in the browser.
This is true for all category and search listings on the site. The left half displays the listing, while the right the currently selected item on that listing.
This means that you get all information about an item as its product page on eBay is displayed right away which in turn means that you do not have to switch between listings and item pages anymore.
This works best if you work on a large computer screen as two web pages need to be displayed next to each other. While there are no size restrictions, you will notice that you need to scroll a lot if the window size is too small.
The extension displays a small Fusion Toolbar as an overlay on the page which you can use to change its behavior. Here you can modify the size distribution which is set to 50/50 by default, toggle filters on the listing page, or add pages to your favorites to open them again at a later point in time.
The favorite system is internal and not linked in any way to Firefox's bookmarking system. The extension will not only remember the pages displayed but also the layout of the page based on changes that you may have made.
The preferences provide you with options to change other display related features such as what to display on the screen or colors used for windows or posts.
Ebay Fusion works if you have enough screen space to display two websites next to each other on it. The extension does not seem to be compatible with NoScript, as selected article pages were not displayed if it was running in the background. Other than that it seems to work as advertised.