I have read a few so so reviews mainly saying its not much of an upgrade from the 400. But I do like the dimmer tail cap. I use my NM400IR with a NV scope and the dimmer would be great to tone down the white out. Sometimes you wish you had a few more modes then the three modes on the 400.
I sent them an email asking can the tail cap be used with the NM400 or NM800 no reply as yet.