I'd thought I'd add my 2 pennies worth to this thread. I've been flying my keelback almost exclusively for the last few months, I believe it's my favourite ship in the game.
It's because it's not the best at anything, but can do everything, and most people hate it. It makes me think on how to do things in game, to compensate for it's shortcomings; you just can't blast away at everything in a hazres but have to choose your targets and time of attack wisely.
So, I use it for combat (PvE of course) and I don't worry about PvP players as I suck at combat so no matter what ship I'm in I'd die anyway.
I use it for missions, general material gathering and exploration.
My exploration version has a 37ly range and everything on board for long term voyages (no fighter bay as I tried exploration with a SLF and didn't get on with it).
It runs very cold; approx 16% heat running in deep space so no need for heat sinks.
The next one I'm building is for PvE piracy, I want to commerce raid local fed and Imperial systems (for RP reasons). I plan on stripping shields with the SLF and use cannons on the KB to module snipe the power plant. Well that's the plan anyway, how well it'll work time will tell.
Finally, I hope one day FDev will bring out the raider paint job for the KB, I think it would look excellent with rusty panels etc.