I've reverted back after trying each build since the beginning of the Insider Program for Windows 10 Mobile. I keep the build for a minimum of 3 days, and a maximum of 4 for every build up to 10581.
Since 10581, I don't even want to consider going back. I love it. It's every bit as smooth and responsive as 8.1 for me on my Lumia 640, and battery life is nearly the same as well. There are features in Windows 10 Mobile that I simply do not want to give up by going back to 8.1. Features like dictation everywhere I can type. I use that excessively as I am rarely in crowds, and it works very well for me.
Now with the TH2 release of Windows 10 on my Laptop, I'm loving the missed call notifications and being able to send texts through my phone. I can't do that with an 8.1 phone, and I really don't want to give it up at this point.
There are no bugs causing me issues on this build for my device. I don't have app crashes. I don't have loading and resuming issues as bad as on 8.1. I have access to a few apps that make a big difference for me that I can't get on 8.1, like the touch Office apps. I like the integration of Skype and Messaging. I like Groove music better than Xbox Music. I like the new Alarms app that includes the world clock, stopwatch, and timers. I love the new Outlook Mail and Calendar app. The new Mail now has linked inboxes. I'm happy, and it is so much easier to use in 10 than in 8.1.
There are a lot of things I like. While I feel I have had valid reason to revert every time before, things like show-stopper bugs for me, I am not experiencing that this time around on my device. The only issue I have is it doesn't show "storage space" properly, but that really doesn't make a difference for me at this time. I also know that Gabe has announced the next build has that fixed.
I for one am looking forward to the next build and further enhancements and stability it will bring, though 10581 is plenty stable enough for me at this point.