On the downside like many say they can be quite loud, but most of the noise actually comes from people 'bottoming out' the keys. That need not be the case with mechanicals. Once you hear the click, your keypress is registered. So after a time with some practice, even blues can be fine around spouses.
A GREAT resource for all things related to mechanical keyboards (and a cool community in general, yes I am a member there) is http://geekhack.org.
If you are already using a Kinesis, you won't get much out of a Majestouch - They're as straight as an arrow.
Black: linear, hard, no sound. Brown: tactile, no sound. Blue: tactile, clicky sound
I use KBC Poker with red Cherry. Light, linear and no sound.
Not cheap, but a seriously nice piece of kit.