Excellent in all respects. The hotel is 10-12 minutes on foot from the main train station (Hlavni Nadrazi) and catty-cornered to the smaller Masarykovo station (where the planned rail link to the airport will terminate, assuming it ever gets built). There's also easy Metro access--you can enter the Namesti Republiky subway station around the corner without even crossing the street--and six different tram lines stop in front of Masarykovo.

The property lies just east of Old Town proper, about a 10-minute walk to the main square. Wenceslas Square is also ~10 mins by foot along Na Prikope (a pedestrianized street) lined with interesting Art Nouveau buildings.

Fairly smooth, with no wait. (The front desk seems to be well staffed; I don't think we ever saw a line there.)

The FDC remarked on my DW's status and gave us a sheet with info on Exec Lounge access. No mention of breakfast option in the restaurant until I asked (answer: yes). Also, see below re room.

Our king BR was comfortable, with good work area, built-in ledge big enough to hold two roll-aboard suitcases, and well-designed closet/shelf space adequate for two adults. (Plus an immense LCD TV we never turned on.) Excellent fit & finish; no visible wear in the main room. Blackout curtains were only so-so; center section was made of non-opaque light-colored fabric vs. darker outer sections.

The bathroom was good, with an Italian-style tub/shower (fixed glass half-partition) and a decent amount of counter space. The sink had some minor damage that didn't affect usability. Large, plush towels^. A few small shortcomings: ceiling fan wasn't working, toilet is installed oddly close to one wall (so your shoulder is right up against it), no non-slamming seat/cover on toilet, and no shelf in shower for soap/shampoo.

One big knock on this room? It looked out onto a grubby interior courtyard. My DW called to ask if there was one with more agreeable views & was told no. (That struck me then, and still strikes me, as a BS answer. Yes, the hotel was fully booked, but it's just not plausible that at 5:30pm they had zero unassigned rooms--including non-Exec-floor, non-suite rooms--with better views. It also raises the question why the hotel didn't pre-block a better room, given that we'd made this reservation months earlier.)

Another fail: the two complimentary bottles of water were nowhere to be found. (Contrast this with the Hilton Budapest City the previous week, where as a mere Gold member I found water, two splits of wine, and some petit fours waiting for us in the room when we arrived in the early evening.) This was cured only after my DW mentioned it to the lounge manager.

Good. Most importantly, they respected our DND door hanger regardless of the hour.

Worked fine, both in room and in lounge.

For general comments on breakfast options, see this post in the master breakfast thread.

For overall comments on the lounge, see this post. (TLDR: pretty good except that it's rather close quarters and at times the service staff are over-attentive to the point of intrusiveness.)

Elevators were very quick to arrive. Having CNN going on a big screen on the car's rear wall was not especially welcome.

More than once when I asked to break a bill, the FDC told me there wasn't much petty cash & she needed it to deal with guest payments. Management needs to do better anticipating this kind of routine request.

The positives very much outweigh the negatives, and I'd stay here again without hesitation.

That said, I don't think expecting better Diamond recognition--especially delivery of a basic amenity such as bottled water--is like demanding a helipad and room for a giraffe. After an equally long stay the previous week at the Hilton Budapest City, where I got much better treatment as a mere Gold, this was a disappointment.