I agree with this mini-review completely "(TidBITS: Coda Plays Web Developers a New Tune". I've been using Coda for a couple of days now, once to add some feature on FP and once to mock up a site for testing an idea. Both times I felt like it was really cool but lacking a few important features--
or just got other things completely wrong actually that's not true, I don't know why I said "completely", I think I just don't work the way Coda wants me to work and it's irritating because it's sooo close to being my favorite app of all time.
The interface has a few surprises that confused me. The top level "view" buttons seem to be doing double-duty as noted in the TidBITS article, and I found myself lost a few times while flipping through tabs. Why would I ever want to see rendered, plain-text CSS? These things seem just an iteration away, so I think they'll figure it out.
I think it all comes down to the fact that I no longer build sites straight on the production server. Any project, large or small gets an SVN repository and a local Apache server (w/MySQL + a doctored /etc/hosts file to mimic the live server). I think Coda would have been essential seven years ago when I lost the ability to use Homesite on my PC when I switched to OS X, but now it only takes about 10 minutes to set up a complete development environment that mimics my production that I can build everything in my own sandbox, commit changes, then have them available when I get to the office.
So will I buy Coda? I think so. I prefer TextMate to SubEthaEdit and I rarely edit things directly on the server, but there's something about Coda that I know I'll miss once it expires. Weird, huh?