It was good for a bit, then 1Password broke and I accepted that my Slack messages were never going to load.
It's a dev preview. There is no reason to use it as your main browser. There isn't even much point testing your site in it, since you can never tell who's responsible for something being broken, and it becomes more a test of how production-ready the preview is, which is a really pointless metric. The only real reason for its existence is so we can all track progress in benchmarks, and for this story to get publicity when all us browser nerds check ES6 compat and then try little code snippets in the console.
If you want the cool purple icon, copy it to to Safari 9. That's what I've done.
Ah if 1Password doesn't work, that's definitely a blocker for me. I could always copy the usernames and passwords from the app, but I don't think I need to test the latest and greatest features that badly.
I don't think I'll be able to handle any instability in that right now. My primary development focus doesn't involve web development so having the latest and greatest browser won't benefit me that much. I do want to try the latest features, but I have patience and can wait a few more months.
I tried for about a week. My complaints with it were the same i have with base Safari, but TP specifically worked fine. No unique issues despite using it as dev platform and a consumer browser.
I wish Safari would have the same incognito mode as Chrome's. Currently, tabs in the same incognito window do not share sessions so you have to log in again on every new tab.
I've been using it as my main browser since release. I've noticed two things:
1) With gifs, Safari TP will loop the first few frames (or whatever loads quickly) and loop that, whilst the remaining frames load, but then never update to looping the entire gif once completely downloaded; refreshing doesn't correct it, just focussing the address bar and hitting to load the gif from cache.
2) Math.random() returns the same result the first two calls on page load.
It is my main browser. Last week there was an update that bricked it. I had to redownload it from apple.com ignorer to get it to work. Other than that it is very good, can't really tell the difference between it, webkit nightly, and reg safari (I don't dev on bleeding-edge though).
I'm currently using it; some sites that serve popups can cause the webpage to disappear, prompting the back button, but other than that it works great.
I changed the icon out with the original safari icon though, personal preference, and set it as my system default web browser.
I did use the 1st release on a daily basis, but I had some problems with it (few websites misbehaved). I may revisit it since it's already at its 4th release and they fixed a ton of bugs judging from their release notes.
