I took my family to Belgium and the Netherlands for vacation over the Thanksgiving holiday, and of course stayed at Marriotts. Two of the 3 properties we stayed at were great. The Hague Marriott in particular was fantastic. Their team was fantastic, friendly, and always offering to go above and beyond.
Unfortunately the Executive Apartments in Brussels were terrible. I had issue after issue with them, and would highly recommend avoiding the property. I thought this would be a great option as we had 4 adults and 1 child, so the 2 bedroom apartment was perfect. Unfortunately the problems started right from booking. Despite booking on a Citi Prestige card to get the 4th night free, Marriott somehow charged a different card, and it was quite a challenge to get them to credit one card and charge the correct one. This didn't even become an issue until 1.5 months after booking as they somehow waited that long to charge me for a "prepaid" rate. The management was slow, but eventually got it resolved, and offered Concierge lounge access next door at the Renaissance as an apology. I appreciated the gesture, but I was shocked when I found it to be the worst lounge I've experienced in any Marriott property. It was quite small, but the real issue was a very unhappy lounge attendant. Twice she tried to turn us away at 10am because breakfast ended at 10:30am. She offered no compensation, and merely said to go to the restaurant downstairs. She was not even polite about it. On top of that, they billed me a second time when I arrived. Again it took a while to get it credited.
My only other stay at an Executive Apartment was in Bangkok, and it was amazing, like most Marriott brands. I was really disappointed with this property and staff. They certainly didn't live up to Marriott standards with many problems that most would categorize as "dumb problems" that should be easy to avoid.