Over the years, I've always touted ACDSee as the best image viewer available for the PC. When I started using it, it was happily at version 3.1, and was a fast, intuitive image browser. I'm now using version 6.0.2, and I'm unhappy to report that it has started bloating beyond necessity. It's full of features that most users will just never use, it's slow to start up, and it doesn't take color profiles into account when displaying images. It also fatally corrupts EXIF data when doing so-called "lossless" rotation of jpg images. DO NOT use ACDSee to rotate your images. According to Chris Breeze (the author of BreezeBrowser, an excellent program), who has been helping me to troubleshoot some of its problems, this is what ACDSee does:
"What appears to have happened is all the portrait orientation shots have corrupted Canon MakerNotes and this is causing BreezeBrowser to crash. ... I've added a "sanity check" in BB which should prevent the problem. ... It appears that [ACDSee] is taking a JPEG with Motorola aligned Exif and is trying to rewrite it as Intel aligned Exif but is leaving the MakerNote Motorola aligned."
So be careful when you rotate images using ACDSee. It's fine for source images that are Intel aligned (not sure which sources write Intel aligned EXIF, though), but since Canon apparently uses Motorola aligned EXIF, I'm out of luck.
I've switched to the fast, free IrfanView for basic image viewing (what I have associated with image files in the operating system), but I still have to use ACDSee for actual image browsing. When Breezebrowser has full-screen viewing and drag-and-drop copy/move, I'll no longer have a need for ACDSee, and will happily uninstall it from my system.