I really like the Sheraton in Warsaw. I actually always book the club floor- which is only usually 15 EUR more per evening. They have very good SPG recognition. For me the location is great- but I suppose it depends which companies you are working with in WAW. The Westin is nothing special- but others seem to like it. I have stayed at the Bristol- the actual building in my opinion is beautiful- and the old town is very close if you happen to have free time. The lounge for me at the Sheraton makes this a much better bet- the staff are extremely knowledgeable and can help you with translators, restaurants, car services- whatever you need (really very good). In terms of in room welcome- they always give me a very good bottle of red wine and a bottle of San Pellegrino every day- I think this is great. On the upgrade front- I could be wrong but I don't believe they have very many suites- even on the club floor. The big rooms overlooking the park are fine for me.