The reviews are all true - this place is fantastic and in one of the best locations in Bangkok if you're there to shop.
By the end off the trip your feet will be sore, and your fingers will gravitate to the numbers 2 and 8 by heart (level 8 is the pool, gym and everything else you can think of and level 2 is the entrance to MBK). There are miles and miles to explore just in MBK and when you've seen all 7 levels, the skybridge at Tokyu will lead you to the skytrain and then to 3 or 4 more megamalls across the road. You are only limited by what your feet can handle.
My MBK tip - head to the food court on level 6 rather than the overpriced bland tourist fare on level 4/5? You'll get authentic hawker style food for dirt cheap prices on level 6. But if you want a $6 ham and cheese sandwich rather than a bowl of duck noodles for $1, go down a level or 2.
One thing I will say about the location is that is gets dead really early in the night. Shops at MBK start shutting around 9 and the area (including Siam square is dead by 10:30). So if you like nightlife more than shopping centres you'd be better off staying elsewhere. However, a 5-10 minute walk to BTS and you can catch a train to wherever you like.
In short, this is a wonderful hotel with no discernable flaws. Except perhaps, it is pricey - you are paying for location, location, location!
Would I stay here again? No. I came to shop and did MBK to death. There are cheaper options for the same opulence in serviced apartments dotted around the city, many near a BTS station. And if I needed MBK again, it's always just a skytrain away.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC.