That's a good question around here! /ubbthreads/images/graemlins/grin.gif
I think the term tactical is one of the most mis-understood of all in the flashlight world, simply because there are so many definitions.
On one hand, I think the concept of calling a light such as the Surefire E series tactical is mis-labeling them. Yes, they may have a tactical style switch on them, but to me, they are no more tactical in nature than an Arc or similar. They simply borrow a tactical switch from the Surefire M series which I would qualify as tactical. (I'm really only using Surefire here since they have an obvious tactical / non-tactical lineup of lights IMHO).
Now... one might ask why I would consider the M series tactical and the E / L series non-tactical? /ubbthreads/images/graemlins/confused.gif In my mind, a tactical light consists of one which is meant for use in conjunction with a weapon. Now this is rather specific, but the Surefire M series fits this bill. They are engineered for a specific grip to use with a pistol and they have optional mounts for rifles and shotguns. In my mind, there are very few tactical lights, and a lot that borrow useful features from those that truely are tactical.
Personally, I love some of the features of tactical lights such as the tailcap buttons. The way I use my lights, this is more convenient for me since most of my use is momentary on / off. However, I really don't need a weapon mounted light, nor the tactical grip on the surefire M series. However, with all the flashlights out there, I'm sure there is something for everyone!!!
Just my $0.02. I'll be curious to see how other's answer this post.