I'll second that.
I've had very good luck with my conversion on my old MBP so far. I have a late 2009 kicking around the house, basically a web browsing computer or backup machine if I leave my newer model in the office, etc.
Since I couldn't get the latest macOS on it I figured I'd just wipe it and install a Linux distro- all told I was maybe an hour into the process and had Ubuntu 16.10 running like a champ. The built in Ethernet was a life saver because I had to replace the WiFi drivers and there were a few power settings I tweaked.
A few weeks post install I've tweaked touchpad settings and various other things, except for the WiFi, it worked nearly straight out of the gate, and it was certainly functional immediately post-install.
Known limitations that affect me are pretty much limited to Thunderbolt hotswap (you've got to boot with the TB hardware plugged in), lid close/sleep is pretty finicky (I feel like this has always been the case with every Linux laptop I've ever run), and the iSight drivers for the built in web cam have some issues therefor preventing some smart screen dimming functionality. If I actually took the time to patch the drivers this sounds like it's resolvable but I really just don't care.
Battery life is tough to gauge because it's so old and I didn't benchmark it pre-Linux but I'm getting about 2-2.5 hours out of it while writing code. Obviously not great, but I doubt I was getting that much more w/ OS X. This machine was my daily workhorse for a couple of years, it's got plenty of cycles on the battery. With auto screen dimming or GPU optimizations, this could likely get improved.
Really, the only thing I'm finding now is that I'm not a huge fan of the default Ubuntu 16.10 desktop and I'll probably start hopping distros since it's been a while since I was running a Linux desktop as a main OS.
I would say that from a completely subjective standpoint it feels every bit as snappy in standard use as OS X did and it will likely keep this machine quite useful for as long as it holds together.