I've only had S1 for about a week now so I can't really comment too in depth. I had tried the demo when it came out and was fairly impressed. Then I sold my Ensemble and bought the Firestudio Live mixer. I love that thing, best purchase I've ever made. So, anyway, I got the upgrade discount then and decided to go with the full version of S1. Functionality is obviously not on par with Logic but I'll tell you what I like. During the whole time I tried the demo (on and off for about a month) and the past week with S1 I have not had one crash. It just works! That is what is so refreshing to me. It's fast, sounds great, looks good, and it just plain works. It is obvious the code is new and they've done a great job. I also love the interface, clean, a bit modern, but not too much.
Logic has been my main DAW for a long time, but I also have DP6 and tried a couple stints with Pro Tools. Every one of them has something that drives me crazy, but I have always come back to Logic. To be honest, I have seen enough of S1 that Logic will be my secondary app now. I still can't live without the hyper editor for some things. But 80% of the time I will use S1 for now, maybe more as it develops and the midi gets stronger.
I would suggest trying the demo for yourself rather than taking anyone's word for it. The thing that sucks with the demo is you can't save, but you'll get a good enough taste.
And as far as I'm concerned, Presonus has been on a roll lately. They hit the perfect price for value/quality point and they keep coming up with fresh new ideas it seems.