I stay quite a bit at SPG properties in Europe and Asia, and find the upgrades are usually quite good - from the lowest priced internet rate at spg.com to various suites, including signature suites. I find at check-in there is a real diligence to writing down your current SPG points total and asking about SPG amenities. Interestingly even during a recent stay at the 4P SFO I was upgraded to a "Jacuzzi Suite" which was nothing more than a regular room with a jacuzzi tub, but still an upgrade.

For me SPG has been the only hotel program worth joining based on upgrades and ability to redeem points when I want. Hopefully you will have better experiences in the future.