Well it's a great app for the iPhone, so I'm sure everyone thinks that, by association, it'll be great for OS X.
So far, I do like it, but I wish they would add a few things. I can't view my favorites in it. They also don't show an icon badge when there are new tweets. It lights up in the Menu Bar, but I'd prefer a badge. Other than that, I like the intuitive nature of the app. It also supports multiple accounts, which is nice. It's ad supported, so it's similar to Twitterffic there. It's just, overall, a very smooth experience... but still not perfect. I'm using it for a few days to see if it'll replace my Twitteriffic use.