I am pretty sure that most of the responses here will be from enablers.
Ask yourself exactly WHY you 'need' this light?
What lights do you already have? Do you just have cheap crap? If so, the TK40 is a fantastic choice, as is the cheaper itp A6 Polestar (which is more floody, less throw). If you already have a slew of good lights though, what will this one give you that the other ones don't?
Since they use AAs, you can get a charger (get a 6 or 8 port one hopefully) and a bunch of eneloop rechargables. You can also use these around the house for other things.
This is nice because having 18650s laying around is totally worthless, except for the flashlight.
You might want to consider an EDC or every day carry light. I carry an itp A1 on my keychain. It can crank out around 250 lumens with a fully charged RCR123 battery and is 2.3 inches long, 0.8 inch diameter. With this light, I always have it handy and I havent really needed my 'main' light.
For 32 bucks (stainless) or less, this is a nice way to go. You can buy a big pack of CR123 batteries and not have to worry about a charger IF you don't plan on using it on a daily basis. Otherwise, you might want to get a charger and a RCR123 or two.