Despite the bloat and all the people who hate it, I'm still using Adobe Reader to view PDFs in Windows. Recently, it was slow on one huge PDF on my laptop, so I decided to try out some alternatives.
Sumatra PDF was pretty good and a bit faster, but zooming wasn't as user-friendly. I didn't like Foxit Reader's user interface. It seemed like an old badly designed Linux application. PDF-XChange Viewer was pretty good, but it also had an inferior zooming user interface. The biggest problem was that all three had slow search in large PDFs, without acceleration via saved indexes like Adobe's Fast Find.
It would have been nice to switch to something leaner, but it's not really a problem. I found that disabling 2D graphics acceleration in Adobe Reader resolves the performance issues on my laptop.