I have stayed at this hotel a few of times- here is my take on it:
-They may offer you a suite upgrade on checkin- although this has typically happened when I have a reservation booked direct with Mariott as opposed to through a website like asiahotels.com/priceline/etc. If you can get a suite for an extra $35 or so it is worth it.
-The pool area is only sunny in the morning- if you want to work on your tan plan this into you schedule.
-The steak house is the best in Bangkok by far.
-You are very close to the skytrain (one block walk)- use this to get around as it is far more comfortable and relaxing then a taxi.
Let me know if there are any questions in particular you may have.