This would be a fantastic solution to the bug-reporting dilemma, because it shortens the cycle.
Consider the following case, of a technically skilled user running CUT.
1. User finds bug/issue/missing feature/suggestion in a particular app.
2. User files bug report.
#Because this is CUT, not stable, the bug report is valid and useful
#to the developers, without them having to utter the usual,
#understandable "but are you running the latest code".
3. Bug gets fixed in upstream.
#User gets the bugfix in a reasonable timeframe; this means he benefits
#from better software, and it's highly motivating for him to continue
Contrast 2 other, more typical cases.
(a) Stable distros. Most showstopper bugs are ironed out. But there are always some that remain. Frequently, these are fixed upstream, but never backported. And if the user files a bug report, the devs often find it not-useful.
#User is never able to run "perfect" software; he lives with one set of
#bugs for 6 months, then upgrades distro version, and gets another set.
(b) Unstable distros. These are unusable as a daily system for the vast majority of users, because there is frequent critical breakage.
#The majority of the talented Linux "eyeballs" are thus dissuaded from
#working where they can do the most good.