Darnell Clayton of BloggingPro has published his list of questions you should have answered before you spend your hard earned cash on a plugin. While most of his questions are good ones, I’d say one of the most important is the aspect of support after you pay. Some commercial plugin providers have switched from unlimited support for the lifetime of the product to yearly subscriptions. For example, a plugin may cost $50.00 for the initial purchase which includes a year of support and upgrades but after the first year, you can opt to pay $25.00 for support or only the upgrades. So far, I’ve had great success with the money I’ve spent on commercial plugins but thoroughly do your research before you spend anything.