The ThinkPad series (T400s, X1 Carbon) has the best Linux support; kernel developers often use them. But they're out of your price range. Maybe you can find a deal on a T400, though?
I've kept the SSD as the boot drive and replaced the optical drive with a 1TB 'SSHD' (Seagate's SSD/HD hybrid).
I've also upgraded the RAM to 16GB.
Disk/RAM upgrades are possible to do 'free' if you already have parts. I 'downgraded' from an X1 Carbon just so I could do this, in fact!
Keyboard: Great for most dev work, though I preferred the layout on the X300 I had before.
Pointing device: I get on well with the Trackpoint and turn off the touchpad.
Screen: Okay. 1600x900 is acceptable as a resolution (though I'd like a high DPI screen next time I buy a laptop). It's readable enough but isn't beautiful.
Battery life: Awful. Probably not helped by the slightly used battery or the 16GB RAM. The second drive tends to be spun down (it's for occasionally-used / bulk storage only) and I tend not to be working the CPU hard. I just plug in.
Linux support: About as good as you'll get, which means that it almost works flawlessly, but will still annoy you.
I've tried Linux in a VM too. Still some problems there. I seem to remember I couldn't just suspend/resume Windows, because Linux would lose its network connection and not get it back without a reboot.
To be honest, I can run everything I want to in Windows, so it's actually easier to do dev work in an OS where everything on the laptop works, and just ssh to Linux elsewhere when necessary.
EDIT: Removed mentions of OS X and Macs!
Speakers: Awful. I don't care too much. Fingerprint reader: Really handy when you're often closing/opening the laptop, but haven't tried it in Linux.
Windows 8.1 runs perfectly and seems really fast and smooth, but if you run Linux (I've used a couple of dists, both with KDE), you see how much snappier the Linux desktop feels. Apps seem to open before you've clicked their icon!
Anyway, there is one thing that bugs me: If I press the bottom edge of the space bar (especially on the left side) it doesn't always register. Is this just my machine that's defective, or is it a problem with the design? Does it happen with yours as well?
(Usually when I'm typing I hit the spacebar more or less in its vertical center and it works fine, but if I lean back and rest the hand below the keyboard, this problem tends to occur.)
When it comes to the screen, the resolution is OK (holding off on high-DPI is probably better until software support improves!) but viewing angles, colors and black levels are pretty bad. That's apparently one of the things they fixed on the T440s (with an IPS display).
No problem with my spacebar. I suspect you have a dodgy keyboard. I haven't looked to see how the spacebar is held together in this model, but it might just be dirt so you may get away with pulling it off (don't say I told you to do that!) and putting it back, but, well, at least a replacement keyboard is cheap and easy to fit.
The 'will still annoy you' comment comes from my memory of stuff not quite working 100%, but I really can't remember what was up now - perhaps it was just when it was in a VM that there were problems. If there was something broken, though, it was probably wifi. That seems the most common problem I have with Linux on laptops these days.
Will give Debian Wheezy a try and see how it goes, thanks!