I've tended to use every major MythTV version number since 0.19 and I upgraded from 0.26 to 0.27 a few months ago. OTA ATSC recording is perfect as always. Feeding the mythbackend over USB are 2 x Hauppauge 950Q ATSC devices for OTA and one Hauppauge HDPVR box for recording from other devices and formats.
I run a separate mythbackend on a headless 4-core Linux machine that is also a router, firewall, squid cacheing proxy, cacheing DNS server, DHCP, NFS, NTP, SQL, and print server. It does all that without skipping a beat or getting warmer even during mythtranscodes.
I have a dedicated mythfrontend HTPC which outputs 1080p video and DD5.1 audio and is connected to the mythbackend over gigabit ethernet copper. I can run a mythfrontend on my Linux notebook but the performance hit over WLAN makes it a bit cludgy so plugging in the gigabit ethernet copper solves that pefectly. I haven't tried mythfrontend on my FrankenMacBook OSX notebook yet (build from 2 dead ones) but I might give it a try just to say I did.
With each new MythTV version the setup items that show up or disappear take a bit of getting used to, especially when the documentation has not caught up yet. Also the data shema for the mythconverg database changes with each version, with no means of reverting unless you've saved an untouched copy. If you ugrade the mythbackend you must
upgrade any and all mythfrontends to the same version and schema. I run MariaDB for mythconverg and it has been bulletproof for stability and speed.