I have an E2DL myself. It was the first high quality LED light that I purchased. I don't know much about modifications, but I will say that out of the box, it is an excellent flashlight. Definitely very impressive if you're used to more common brands.
It has an impressively long runtime on the low setting, at a brightness level that is perfectly suitable for reading or searching for your keys in your tent.
The high setting is pretty bright. Just shining it on a reflective surface is enough to make me squint, provided I'm standing close enough. Switching between output modes is easy too.
It's pretty light and sturdy for it's size; typical surefire. Also probably overpriced - in my opinion a fenix light is almost as good for quite a bit less. As you probably know, the E2DL is designed for self defense, but i've never felt the need to use it in that capacity. I realize that the slightly flanged edges make it a kind of pseudo kubaton, but frankly, hitting someone with a tough, solid piece of metal (i.e. any similarly sized flashlight) is probably going to produce results.
That being said, I think it's a great light to start out with. It's not going to break on you anytime soon, and it's a good balance of novelty and utility.