It's pretty good. Lilypond suffers from the overly false modesty that all open source projects have, which is to declare development versions 'unstable'. Technically this may be accurate to say, but in practice I have found the development versions over many years to always be outstandingly good, a real tribute to the excellence of our developers. It's the same with version numbering in open source: modesty demands that some programs sit at version 0.9 or so for up to even decades until proved utterly error free beyond all earthly standards.
Where's the harm in it? You can always install multiple versions side by side.