Hi Lauren,
My husband and I have been staying there since the year they opened and, while we occasionally still do a night on the Strip, we primarily stay at M now for a stretch of four or five days.
It is a lovely, serene property.
Even though we're only there about five times a year (so prob about 20-25 nights), the bartenders remember us and know our preferred drinks before we even say hello; the staff in general is extremely friendly; the video poker is solid (the tables always seem quiet, but since I don't play them, I can't really comment!); and while they could use another 24-7 restaurant (still lamenting the days of Hash House A-Go Go), the food options are overall very good (esp the buffet).
As for the rooms, they're really, really nice. Spacious, nicely appointed (I still complain that they need more outlets near the beds since everyone has a phone now, and they seem to be working on that), bathrooms have double sinks and a TV screen embedded in the mirror, the toiletries are good quality.
It sounds as if you visit Vegas as much as I do (I take a couple of additional trips with friends or by myself), so once you get in their system, you will be treated very well with comps. Oh, right, their cashback/points/comp system is one of the most generous I've encountered.
The only thing I DON'T like about Marquee Rewards is that they re-evaluate your status every six months, so if you're only out a few times a year, it can be tough to maintain a certain level in such a short span. But I've found that the Tier Status is more beneficial to locals with their weekly giveaways of things like bottles of wine and crock pots - nothing I need to schlep in a suitcase!
We've had a host since or earliest stays there and our current one is a great guy. If you want to PM me, I can give you more details about him.
Hope this helps! I love to be a cheerleader for M - but then again, it's kinda nice that it's sort of a well-kept secret!