Reviews are actually pretty good with regards to that. The complaints I have seen is that the battery dies after a couple of years and is not easily replaceable. This would mean a new keyboard every couple of years.
The K750[1], which I've been using for a month now, works in very low light, and on a full charge the internal batteries should last without light for "up to 2 months". It's impressive. And a really nice keyboard to boot!
