I'm SPG-Plat. I'll be in Warsaw April 2-4, 6-9 2009
Sheraton, Westin and Le Meridien are the options.

My needs: Near train station; club room(!); real (modern/updated) fitness equip, (steam/sauna/jacquz); and complimentary computer (clubroom?) to avoid bringing a laptop. Also, clean and quiet room. I don't care about the breakfasts.

I'm not going for touristy reasons. I'm doing research and work, and, I'll have a guide/translator.

I'm leaning towards the Westin, then the Sheraton, followed by the Le Meridien. Using the SPG search tool with amenties, only Le Mer lists a club room, but, I know the Sheraton has one. Same issues with fitness too.
Reviews on TripAdvisor lineup that way too.

Promo rates are incredible, and, with the PLN lowering, it's a deal at any of them.