Stayed here recently and left with mixed impressions. It's certainly not bad if you're chasing Hyatt nights and can be a good value on points, but not sure I'd stay here otherwise. I've always stayed at the Westin in Berlin in the past, which has its own quirks but overall I think I prefer, as I've always gotten suites there that I found a bit better laid out than the one here, and IMO it's a bit better location.

The less good

The standard suite, confirmed with a TSU, is a full suite with a door separating the living room, but it is not very large and a bit awkwardly laid out. There were also some odd choices made in designing the bathroom, including a nice enclosed shower/tub area but then only a basic standard showerhead. In our suite, the shower water temperature also fluctuated randomly.

The air conditioning was also just barely keeping up on some hot days and definitely may not be up to the standards of some Americans. (The always-on heated bathroom floor seemed to be actively thwarting its progress.)

Berlin is sprawling so I'm not sure there's a best location, but this probably isn't it ... the surrounding area is very sterile and boring. Potsdamer Platz is an okay transit stop to be near but we did need to transfer lines for most trips we ended taking, though again I've found that pretty common in Berlin. (The Westin's immediate surroundings are kind of sterile and certainly very touristy in their own way, but the trains that it is close to are more useful in my experience, especially with an easy walk to Friedrichstrasse station a few blocks away.)

I personally didn't love the gym, though others may be happier with it. It's not very large so could get crowded easily, and most of the strength equipment is of a strange variety that I've come across at other European hotels that is ... resistance-oriented? I don't know how to describe it.

No specific complaints with service, but it was very ... German. To the point and not overly friendly.

The better

I did not try transit from the airport (and ended up having an exceptionally long Uber ride due to various unusual mishaps), but in retrospect it would have been fairly easy, even with some luggage, or at least would be if you somehow knew exactly where to exit from Potsdamer Platz station without having been before. (The correct exit is across the southern mainline train station hall from the S-Bahn, if that helps.) A transfer is required but there is good escalator and elevator coverage at the two transfer point options, and Potsdamer Platz station is well-escalatored.

We were offered restaurant or Club breakfast without issue. The Club breakfast is a subset of many of the exact same items as the restaurant, though unless the restaurant is packed I can't see any reason to choose the Club if you have access to both. The restaurant selection is very German, so was a big hit with my smoked fish-loving husband, but there's also enough variety that there should be something for most people.

The evening service at the Club includes a "tea time" from 4-5pm and a more standard evening snacks selection from 6-8pm. The former includes a rotating selection of a few cakes and cookies each day, while the latter is a fairly standard offering with a hot item, some salads, and some sweets. It's not elaborate but we happily made a dinner out of it the first night when we were tired from traveling.