Overall the feeling in ZETA is pretty nice. To my opinion they have made a good follow up on the R5 BeInc. left us. There is room for improvements but I do think that the system can be used on a daily base (I've been using it from day one with RC1).
On modern systems ZETA is capable of doing the work its meant to do, booting a very fast OS, stable and with a descent package of tools and applications to get you started.
I don't see any reason to stay within R5 other then to compile stuff I can't compile on ZETA (and that's because the src is written to be compiled in R5).
The locale system is the best I've ever seen in any OS so far.  (If any capable of doing so in the first place - the people from SkyOS are doing similar stuff only they use xml files for that - and SkyOS has a long way to go until they reach the maturity ZETA has).
As an alternate OS ZETA comes in first place for me, I wont be teased with viruses nor independences for any libraries that are a pain to get installed.

This concludes my ZETA 1.0 review, I hope you enjoyed it.
Being my first review I ever did ... don't shoot me when we meet. ;)