I've got one and like it. Made a difference on my Charger. I have the 91 tune installed right now. Nice improvement in performance and actually improved my MPG slightly over stock. It's not like adding a blower or anything like that, but it does improve the overall performance. It is an improvement you can feel. I return mine back to stock and it just doesn't pull, shift or react like when the SC tune is installed.
I don't plan on modding my R/T anymore than I have (at least that's the plan). My thinking is if you're going to stay basically stock (minor bolt on's), then you might not gain any more with any other tuner vs. the SC. Sure, the soon-to-be released SCT and Diablo tuners have a few more promised user options and are probably going to be more up to date "gadget wise" than the SC, but the SC for what it is and does, is worth it to me. If you're getting it for a good price, I say go for it. You will like it and won't regret it. Of course if you absolutely need (or want) the options that are supposed to be included with the soon-to-be released tuners, then you should wait and spend some more.