With the much-awaited launch of Mozilla Firefox 3, extensions, themes and addons will be a problem.
Mozilla has released many alpha, beta and release-candidate versions of Firefox before the big launch, giving developers time to update their addons. Most extensions work flawlessly, and many more can be hacked to work, but themes and other non-extension addons still remain a problem.
Assuming that you are interested in using compatible addons, here is a quick tip to save you the blushes: use the “Advanced Search” at Mozilla Addons website to filter themes incompatible with Mozilla Firefox3. Click on the “Advanced” text just below the search field to pull down advanced options for search (screenshot below):
This will remove incompatible addons from search results. If you need to filter something other than themes (say, specific categories of extensions, like “Bookmarks”), change the “Type:” to the desired option.
On a sidenote, have you had to sacrifice functionality because of incompatible addons? I have personally had to remove only 4 incompatible extensions, your mileage may vary.