Nothing to add on the Sync yet (though hopefully I will be able to soon), but a little on PF30...
The PF30 BB's are expensive, and the bearings don't last all that long. Agreed.
BUT... You can buy/build/improvise the tools to remove the bearings from the cups very cheaply, and the bearing (in a SRAM BB at least) is an off the shelf bearing from any local bearing supplier for a few quid. Personally I'm happy that with the Sync I am now building up, that it's going to be £6-8 a time to change BB bearings instead of £20 a time to change the whole shebang on a Shimano HT2 (that don't tend to last all that much longer anyway!).
If you're dead set on keeping a 24mm axle crank though, then the Praxis converter BB is actually a wonderful unit, very well designed and executed. Nothing requires gluing anywhere, the BB screws up onto itself forming a friction fit inside the BB shell. Remarkably simple and well executed!
Anyway... Cartridge bearings on an MTB go through a very hard life, and should be considered disposable items IMO. The cheaper/easier they are to replace, the better. PF30 is easily maintainable with a couple of tools, and BB30 (don't get the hate on this either) even more so as the bearings just sit directly in the frame so need no tools to remove!
Certainly, I'd not let something so simple as a BB standard put me off buying my next frame. Only thing that would even make me think twice was if I already had some shiny expensive BB30 cranks, and the new frame I was looking at only had a conventional BB shell.
Oh, and sometime in the new year probably, if you fancy a demo on a medium sized Sync and you live in the Midlands, let me know...