Alright, well I got my D20 last night and well, after 3 sets of batteries (night shift) and playing with it I can wholeheartedly recommend the T25-t.
I am on the verge of disappointed really, especially since I dearly love the D10.
The huge head sports a badly focused LED, so much so that the hotspot looks more like that of my SF L2 with a MC-E stuffed in it than the usual cree pattern. The T25 completely outclasses the D20 in throw, output, runtime, and overall comfort during use.
I am going to keep trying the D20 and see if I can come around to liking it, but has left me wanting so far. I think I prefer my old and abused L2D to it so far. It is not as bright, but it has a tighter hotspot and a longer runtime on high. They both get warm during use, but it take much longer for the L2D to heat up. The T25 did not seem to get as warm.
I do like the clip and the UI of the D20, but it has the battery bounce "glitch" that people have mentioned. That annoys me. This is my 4th Nitecore light. It is the first one to not impress me out of the box.
It was a toss up between this and another Olight and I shoulda got the m20 I think.
If you plan on using the light outside alot or at any distance then definitely go for the T25, indoors, the floodier beam of the D20 might be more useful. The more "organic" shape of the Olight makes it more comfortable to use for long periods of time, but indoors I think the D20 and its ability to tailstand nicely has an edge over the T25-T with the protruding forward Clicky.
I am at that stage where I don't know if I should be irritated or content. Maybe I am missing something or maybe I can learn to like it.