I just completed my first stay at The Cosmopolitan, and my entire family was blown away by what a wonderful hotel this is. We went into it with some trepidation, as our party is not the typical Vegas clientele, and we were especially concerned about online reviews that complained about "twenty-something, new money poseurs" all over the place. Those concerns were unfounded--the hotel staff made us feel as welcome as anyone else, and if anything the clientele here were a little more classy than elsewhere on the strip that we explored.
I really can't say enough about how great the staff was here. Every associate we met seemed genuinely happy to be working there and to be providing service. All of the restaurants we tried were quite good, some superb. The hotel itself is CLEAN, like sparkling clean, which really stands out against even some of the other so-called upscale hotels nearby. Housekeeping was thorough, and engineering responded quickly to two small issues we had--they clearly want to keep the place in tip-top shape and it shows.
If anyone has any questions about the Chelsea Penthouse Suites I'll be happy to answer them. I also became something of an expert in the vagaries of the Marriott Rewards vs. Identity Rewards programs and would be happy to try to help clear up questions about those.
In short, my family and I hadn't been to Vegas in six years; now we're already planning another trip back next year, mainly because staying at The Cosmopolitan was such a pleasure.