We spent about a day and a half at the Vdara pool. For our "pool day" we rented an Escape Cabana. Pricing varies based on month and day of the week so I can't estimate what it might be for you but on a weekday in May ours was about $150 for the day. The cabana rental came with four waters (regular or coconut) and a fruit plate. You do have to ask for the server to bring your fruit plate when you're ready to eat it.
The Escape Cabanas have a "private" plunge pool that is shared between the cabana guests. There are about 5 cabanas in each area so if each one had the max number of guests you're talking about 20 people sharing a private pool. Luckily, our cabana neighbors weren't using the pool too much and it seemed like most only had two people. Who you are sharing the cabana area with will most definitely affect your experience and unfortunately there's not much you can do about it...just keep that in mind.
We came at the earliest possible check-in time and still had to wait 10-15 minutes until they would let us into our cabana. Once we were settled in, I was very bothered by the super hokie elevator music coming from several nearby speakers. The music was seriously awful and I knew it would ruin my cabana experience so I ran over to see if they could turn off the speakers around us. Fortunately, the cabana attendant was super understanding and spent a good amount of time switching speakers on and off until the ones surrounding us were off. This really made all the difference.
On a different day we spent some time at the main pool with the common folk and it was fine--nothing great or terrible about it.
If you're going to spend a full 8 hours at the pool I highly recommend splurging for the escape cabana, particularly if you can split the cost with friends.