As 7.0 is approaching release, a recurring question on the mailing lists is (in its many forms) “how stable is it?”. The answer really depends on what you are planning to do with it, but there are several known errors, bugs and misfeatures which will surely be present in 7.0-RELEASE. If your workload includes some of those, you better wait for the next release before putting a 7.x in production. If not, go ahead: by all means it’s stable enough.
Here’s the list of problems currently known to me, as of 7.0-BETA3. The list is probably not complete (so it may grow over time), and some of the problems listed may not be relevant to your workload, so take it with a grain if salt.
* ZFS is mostly unstable (or at least not as stable as UFS), especially under low memory conditions, on both i386 and amd64
* tmpfs is somtimes unstable in subtle ways (not very repeatable)
unionfs doesn’t work over cd9660 (this one is obscure and only hurts LiveCD makers)
* removing mounted USB drives still doesn’t work (and USB support in general has most of the old problems)
gcc program profiling doesn’t work
java doesn’t work stable with some applications (tomcat sometimes crashes)
* while performance was greatly improved for database-like tasks, there are reports that complex tasks like heavy web applications could have performance problems.
In addition to these, there are some “non-bugs” which get reported often, some of which actually are bugs and problems but they have always existed and people have grown accustomed to them:
* BETA ISO images don’t contain packages (though sysintall offers to install them, and fails with weird errors)
* Support for 3D in X.Org is very limited, mostl due to lack of drivers (yes, there’s a NVIDIA driver for i386 but there’s no equivalent AMD64 version).