Pretty certain it was the Marriott Plat status, as I only tipped after she said she could hook me up with a Wraparound Suite.
If you can get that Wraparound for $320, I'd say go for it - it's one of the best rooms I've stayed in; you can save some money by using the full kitchen and making your own sandwiches/drinks etc.
Using a cashback site might get some money off if you book via Marriott.com though I think the 4 nights for 3 is a great deal...
Make sure you get a high floor - noise problems from the Club are an issue and if you value your rest, you need to keep your distance.
For uncorked, a four night stay Thu 10 May -Mon 14 May, the 1200 sq. ft, Wraparound + 480 sq. ft balcony (flooplan below) is coming in around $350/night, a regular Bellagio Fountain View Terrace Suite averages $250/night:
Venetian/Palazzo would be the back up, but the rooms are quite stark from my experience a few months ago (even the suites), and it's not as contemporary as the Cosmo.