Yes, I have had the KBC-L2S for a couple of years now and it's a very capable device. Not cheap, but eneloop is known for quality.

Unfortunately it has the same problem with the N900 as most other "dumb power sources" (ie USB chargers that are not computers): the N900 will not charge from it if the USB cable does not have its "data pins" shorted.

Of course there are solutions for this (special cables, home made hacks) and my Sanyo now work just fine with the N900. See the threads on this topic, such as this one:

http://talk.maemo.org/showthread.php?t=38230