Well worth it in my book. I paid $300 on sale. I had it tuned 2 years ago (tune only) and loved it. I posted 2 reviews about it on here somewhere. others have as well. I just added the needswings DCAI this summer and then had it retuned by Eurocharge (free tunes for life if to make adjustements for mod upgrades) and wow. I'm done with performance mods on it now. The DCAI and the tune make me happy and you you can't get much more ponies out of it than I have now anyway, even with much more serious money. Car is more responsive and a blast to drive In my view, the tune is well worth it.

Here's my recent review of my tune:
My first and only mod up until now was the eurocharge tune. I did a long write up back on my experience with that back in July / August of 2012. In summary, my initial reaction to the tune was I didn't notice much difference in the low end / take-off performance, at least at first. My experience in the mid to upper range of RPM was..........Wow, yes I noticed it. As I drove it more, I began to notice even lower end lower rpm differences, primarily in shift points. Part of that might have been due to me "training" the tranny. Anyway, I was definitely satisfied with it. HOWEVER, I also knew someday I would do the Needswings DCAI install. I chose the dual because I like the look and the symetry of it. I also know others who had done the mod like it, said it was noticeable and it certainly looks bad *** (IMO). After my install, I coordinated my free retune with Eurocharge to make the computer adjustments to account for the DCAI. Results.......WOW, it once again make a difference. I feel it more in the lower end than before and the upper end is again, very noticeable. I'm very happy with it. The Eurocharge tune / Needswings DCAI combined HP increase is 40 collective HP. I am not going to dyno it, so I have no idea of how the mods translate to the wheels, but in terms of how the car "feels", it feels great. I have chosen not to do the 74mm upgrade. Not sure it makes that much difference and I have heard some have experienced codes after the install. It will be marginal help so I'm not going to bother. I'm done with performance mods. The 2 biggest bang for the buck mods are these so if I want more HP I'll just go buy and SRT. Hope this helps you out. Let me know how your mods go.

UPDATE: Sorry, I didn't answer your question about mileage. Hard to say. I get on it more now than I used to. It's a weekend car so when I take it out it is to "play". That being said, it doesn't appear to have had any negative effect on my cruising experience. It's about the same if not a little better on the highway