Keyboard since I started, I only enjoy controllers for mining or events where I don't use macros. It's just too slow to scroll through the pallete. On a keyboard, even though the pallete takes a second longer to load, you can still fire a macro while that's happening.
For smooth turns with a keyboard you strafe the camera while moving forward. For looking behind you while running, I don't understand why that's a problem, you would do the same thing you do with a controller. Unless for some weird reason you don't auto-run forward while looking behind you.
edit: What Mojo said, not inhibited but less precise. I solo a lot and it's never been an issue.
I admit targetting alliance members used to be difficult on a keyboard. Since they added <stpt> and <stal> that's not a problem anymore.
My friend used to have a keyboard/controller combo, it was awesome till the analog stopped working. This is the exact same one:
http://www.superufo.com/item_photo/item/PS2-0601-L.jpg