It be nice to see some Opensolaris tests thrown in to even it out. After all that is the platform it is developed on. it mighten show much of a difference but if there is an improvement then part of issue could be with FreeBSD implementation.
I'm (pleasantly) surprised that Btrfs is this nimble with such meagre hardware.
The code path of Btrfs (similar to ZFS in this way, I believe) made me think that it was only going to be really useful on VERY large setups. I still would love to see cpu numbers, but I am actually a bit hopeful that this may be a truly scalable fs.
Currently, ZFS under Linux can only be used as a userspace file system via FUSE (zfs-fuse), which impacts performance. This is due to licensing incompatibilities between the Linux kernel (GPL) and ZFS (CDDL):
btrfs is impressive. Chris judiciously selected his feature-set for technical reasons, as opposed silly marketing reasons. I mean, come on, a 128 bit filesystem? What was Sun thinking? That's a bullet point for glossies aimed at managers who don't understand exponents. (Disk storage space has been increasing at a uniform rate of about a bit every 1.5 years for the 23 years that I've been watching. And Linus would probably have a brain hemorrhage if presented with a set of patches for a 128 bit filesystem.) Pragmatic design decisions have allowed btrfs development to progress with remarkable agility.
ZFS means a LOT to Solaris users. Because before ZFS, logical volume management and SW RAID meant Solstice Disksuitie (aka Solaris Volume Manager). And while it worked "ok", it was a real mess and had lots of frustrating limitations.
ZFS looks REALLY interesting if you DO NOT look at LVM and other *ix OS's solutions. So for a Solaris person who knows the pains of SVM, ZFS looks absolutely grand!
With regards to "feature" differences, I'd recommend just looking at the features from both sites. From my own experience, ZFS users tend to be "blind" and unwilling to look at other technologies... they've decided that they're #1. With regards to Linux distributions, I'd say greater than 50% of the so called "top" engineers I've met from Sun haven't used Linux since Red Hat 7.2.
Btrfs is an IMPORTANT filesystem... like ZFS. Btrfs means enterprise like features, like ZFS. However, unlike ZFS, you will be able to use it with a Linux distribution (arguably, you could port it to your own Linux today... you just can't distribute that custom edition).
So... ZFS, IMHO, doesn't bring too much to the table... UNLESS you're a Sun SVM + UFS user... then it's fantastic! I'm serious, UFS and SVM are ugly and have been very, very, very, very, very, very problematic in the past. ZFS came late for Sun and a bit late for the *ix world and N/A when it comes to a Linux distribution.
I'm not saying that ZFS isn't ok... it is ok. But the future belongs to things like btrfs... NOT ZFS.