The (approximately weekly) "beta" updates are generally pretty stable. You can set the update channel to grab Stable or Latest versions, but really there is no notion of alpha/beta here. Features are released, and they are tested by the devs and some additional people. Once seemingly safe-enough, the update is pushed to the top of the latest MC forum board and available for auto-update.
It would be difficult to know what percentage of people use the built-in ripping vs. external. With a Secure rip to a lossless format, that's generally good enough. Two features that people desire (that is not currently in MC) is 1) post-rip file testing (eg. the flac tool's -t option) and 2) AccurateRip (which will probably not happen in MC as the devs feel it is more of a solution looking for a problem).
Re: (1), I've only encountered a couple of file issues over the years of ripping with MC (after switching from EAC years ago), and both of these were likely due to memory CRC errors. Running a flac.exe -t found the errors, and re-ripping the couple of files was not an issue.
Re: (2), if you can't hear/notice any issues during playback, AccurateRip really is a problem looking for a solution.