I would love to run a *BSD as my daily driver on my X220, but battery life is important to me and everything I've read suggests that most BSDs don't perform as well as Linux + TLP,
Performance isn't an issue really even though its an i5. If it is too slow, I ship the problem elsewhere (the feck off great big 24 core E5 HP Z620 in the office).
Sure there may be 10% difference between BSD and Linux but that's negligible these days versus the positives (like being able to just pkg install ruby21 without having to bugger around with rvm or wait three years for debian to pick it up in stable)
I've got a 9-cell battery.
I'm running -current. Now that -current is also offloading rendering to my integrated i915 gfx, I'll be curious to see how screen-intensive work will impact battery.
The joy I get from NetBSD has outweighed various temptations from other OSes. I've dabbled w/ Ubuntu and others, but they're not compelling enough to switch.
If you've got any questions, I'm happy to try to answer.
Windows 8.1 Pro with Lenovo power manager installed via windows update.
Dual boot.
I would check the Lenovo recall page (google it) before paying for one. That's where I got my new one from - they replaced it free of charge ;-)
I'm not really a leet haxor when it comes to fiddling with driver power management and configs. I like linux because I can just fire up powertop and manually switch the config settings to the ones that TLP doesn't flip automatically.
Did you have to do a lot of hacking and do you know if openbsd is comparable in terms of power management?