last I checked some patches for the dealloc empty file problem was being merged in 2.6.30. if you want to avoid it but want some other advantages like faster fscks you could go with data=journal on your filesystems which is a bit slower but also disables dealloc, while still having extents, barriers, and other ext4 benefits. I've been using data=journal on my /home partition without a single problem.

it also depends a lot on what you have in 'production'. a web server that's mostly doing reads it should be fine for. a heavy email server... well.. can you afford to lose email on a crash? I think it might be alright for a server that just does mta but not the fs for the actual mailbox's (with dealloc anyways). database server should be fine, because the database's job is to make sure data hits the disk, among other things. dns servers are a very read heavy so again I would think it'd be fine. so basically you need to watch anything that's heavy write and not to a database, and even then only with dealloc.

still as I'm sure others have said, it's a good idea to wait on new tech like this. some tools don't yet recognize that ext4 is not ext3.

This is the only IDE that's getting my vote atm. since it has a 'fakevim' mode plus a lot of other IDE features. being primarily a vim user having a vim mode is essential (even though it's not perfect). It seems to be pretty good in general, but I haven't used a lot of IDE's, I like it better than VS, Eclipse, and Netbeans, all of which I stopped using after an hour or so of not accomplishing anything.

not knowing the software you're working on why does half the stuff you mentioned matter? don't package for distro's that's their job. release a tarball and general installation instructions, and dependency requirements. the shells are generally posix so one standard, and bash is 99% reliably installed. print engines? besides cups? well there might be some I suppose but most of what I've seen works with cups on the desktop. config files go in /etc sure sometimes distro's lay it out a bit different but you make software do you really need to know where config files are other than your own? if you do just add a line in your config file to specify where they are, you should have one anyway. test, package, and document for 3 distro's right now I'd say fedora, ubuntu, and gentoo. an rpm distro, deb distro, and a source (ebuild) distro. you don't have to offer support. just release and don't reject support requests for it out of hand.