in the less than 24 hours I've been using them, it is easily the single greatest upgrade to my photography ever. Way more important than a camera body upgrade for sure. It can take a boring snapshot and imbue it with character. Now I can only imagine what might happen if I had a great photo to start with.
Be sure to check out Nik's tutorials, while some of them are a bit lame [use this plugin and that] others tell you how to smoothly do your own images from scratch, after a couple you'll be tooling along like a pro I had just gotten this suite of software for our May photochallenge. Wow that was almost a year ago.