Been using this build for over a day and few more hours. Can say that it is stable and works just fine, although Cortana suggestions is still broken for me; it kept showing no suggestions for my region. I can confirm that Cortana works in my region (Malaysia) because it is currently working well in my PC (PC is running Release Preview build) and in my phone during the AU builds. Quite a sad situation as Cortana gives me a very concise overview of local news and updates regarding my football (or soccer) team, as well as general weather of my location.
Also, Outlook Mail & Calendar stopped producing toast notifications in the action centre (can only know if there're new e-mails via live tiles), but I don't think this issue was caused by this new build. It was the recent update to the Outlook app that caused it. I believe it is so because this issue started after I updated the Outlook app, before updating to this latest build.
Other than the above, this build is generally stable for me, and performance is quite nice as well. Battery was good for the first day, but I'd wait for a few more days before giving my final verdict. The previous build gave me stellar battery life for two days, before a full charge lasted me from 8AM - 5PM afterwards (phone left with about 15~20% battery), which for me is quite disappointing since I wasn't using the phone that much; used the phone for about 2 hours only, meaning 2 hours on-screen time, and the rest is phone on stand-by on LTE (was outside the house, so had to use data).