I stayed there last week. It's an easy drive to Disney. We did time it, it took use almost exactly 20 minutes from Grande Vista to the parking lot at Magic Kingdom.
I've stayed at 3 other Marriott timeshares and this place was honestly the worst of the 3. It was still better then most of the non-Marriott timeshares though! The room clearly needed an upgrade. There was rust on the appliances, cracked floor tiles, and mold in the bathrooms. I know they are re-doing the rooms and assume they really let go the older rooms like the one we had. It was not up to the standards we typically see from Marriott. Nothing repulsive, it was just disappointing.
On the positive side, the rooms were very spacious and the beds were comfortable. The staff was great, the room was quiet, and the grounds were pretty (we were right on the golf course). They had free wireless in the rooms so we brought a laptop. We had no problems getting on their network and had a fast connection. We never used the pool since the air was too cold for my taste although the water was heated and some people were swimming.
There's a Publix right around the corner (5 min) so we bought breakfast food to eat in the room.
International drive has a lot of restaurants. Grande Vista has one on-site restaurant which we never got around to trying out. Of the various places on I-drive we tried, our favorite 2 were both located at Pointe Orlando. This is outdoor shopping area located about 5-10 minutes north on I-Drive near the convention center. The entrance to their parking garage is a huge upside down building. This center had all kinds of restaurants and we never had to wait to get into any of them. The 2 places we tried that we really liked were Tommy Bahama's and the Redrock Canyon Grill.
Patty