I want ZFS because its great and it works.
Yes, it eats memory but when 16G costs me ~£100 - who cares FFS.
When I was young I spent £100 (~£250 in todays money) 512K - yes thats K, not M, not G!
I want Dtrace as its fantastic for debugging.
I want it on Linux as I use Dtrace on FreeBSD and Solaris - open + larrys versions.