Let me tell you what I have learned and what I know about alfalfa. It DOES come with some dangers, especially for stalled horses. Since you cannot feed it free choice, stalled horses are MUCH more prone to ulcers when fed the standard 1-2 flakes AM and PM. This leaves them standing a stall 18 to 20 hours of every 24 hours with an empty stomach and they become prime candidates for ulcers.
I agree with you on this. My horse is only stalled at night but since the entire reason we added alfalfa was to put weight on him and he's in a drylot (can't handle the pasture turnouts, he freaks, doesn't eat/drink and colics) he gets a ton of grass hay along with his alfalfa (enough that Mr picky doesn't finish it all).
He does go through a TON of bedding but oh well... he's a very neat horse so I thickly pile the bedding where he pees so that he's never in a wet or smelly stall and I shovel out the wet shavings daily.