I stayed there a lot as a Platinum. Most of the time the only upgrade was to club floor; a few times got a suite (I think they call it a junior suite but it's a bedroom with separate living room). They seemed to have the attitude that one step up (regular to club floor) was enough of an upgrade. The food throughout the hotel is not great in my opinion (except the Italian restaurant which is fine).

I've since moved to the W for my stays and enjoy it better in most regards.

The Sheraton and most of the older hotels are government owned. The newer hotels like the W are privately owned and I think there is a better service culture on average at the privately owned hotels. But with that said, I found the service at the Sheraton to be fine.

Generally it's easy and inexpensive to get a taxi from the airport to any major hotel (maybe except if you arrive at a really busy holiday time). You can pre-book a hotel car but it will cost more.

Also a downside of booking the hotel car is that you have to pay even if you can't use it (e.g, flight change). But if you are merely delayed in the airport you should still get your car transfer.