I stayed here as a Gold a week ago, arriving in the evening and leaving in the morning for an early flight. I booked a river view on a BRG, and I don't believe that I got an upgrade. As an aside, I had to follow up with the BRG team to get the points to post.
Check in was great. The agent who checked me in was a trainee (and super cute), and she offered us some Haribo gummy bears. This was great, since I was going into Haribo withdrawal. I had a bit of trouble opening the door -- it turns out you have to push the door in after inserting your key. The doorknob doesn't actually do anything.
The night before my arrival, I sent an email to the hotel. I didn't receive a response, but, upon enquiring with the concierge, it turned out they'd fulfilled it. I'd asked for a few cheap stamps for my collection, with the cost added to my bill, and they gave me the stamps for free
. He was also able to recommend a good Currywurst place nearby.
The room was spacious, and housekeeping was immaculate. The river view, however, was less than stellar : although we were on a high floor, you couldn't actually see the river because of all the trees surrounding it. The curtains worked fine to block out the light.
Overall, I liked this hotel much better than the Westin, and I'll be coming back next time I'm in Berlin. I'll echo the perspective of the others who suggest that this might not be the best property for your first visit to Berlin : a lot of the main attractions are a bit far (ie not walking distance). There are a few restaurants quite close by, but I didn't get a chance to try them out.