I know this is an oldish thread but the flashlight is still available in stores.
I have one, picked it up on sale for $30ish, and as a flashlight noob I think it's pretty bright for the money. It's got wide spill up close and does a decent job of lighting up the trees ~75 yards behind my house...
I just ordered a TK45, I'm a dog walker as well.
I don't have it yet but if you're still in the dark when it arrives I'll try to help answer some of the questions.
The main reasons I bought the TK45 over the TK40, TK30 ... etc. is the availability of cells (everything I own runs on the same...
Most of the stuff I have runs off the same batteries so I don't mind the battery layout.
Assuming I read the stats right, one thing I like about the TK45 is the longer run times in each mode over the TK40.