I too am a happy owner of Waves Platinum bundle. I notice a huge difference in audio quality when I use my waves plug-ins in comparison to Sonar's plug-ins. Especially on comparisons like Sonitus Compressor in comparison to the Renaissance Compressor. Their plug-ins don't only sound great, but they are designed very well so that they are easy to understand and use.
With that said, I also think the business practices of the company are horrible. For my business, Waves is a necessary evil. If their plug-ins didn't sound so good and if so many people weren't using them, then I would definitely be using other plug-ins.
My experience with support and Waves really varies. When it comes to Pro Tools, they are always fully updated and working great and I have rarely seen any problem with compatibility. They will have their plug-ins primed and ready before releases of Pro Tools. Sonar is a completely different story. As long as I have used Waves with Sonar, I have always had buggy issues from the GUI to multiprocessor engine and etc. It is really disappointing. But when it comes down to it, Waves biggest customers are the Digidesign customers that are forking out the cash for the TDM plug-ins. I know very few Pro Tools HD users that don't own any Waves plug-ins. Much of the Sonar crowd is happy with the stock plug-ins or would purchase the Wal-Mart type plugs before even considering Waves. Therefore, Sonar is an after thought to them. It is sad, frustrating, and infuriating. I know.... I've been there many times.