I have 16MB, and usually have dozens of windows/tabs open in Safari, Xcode, Textmate2, and a few miscellaneous apps. Currently, Activity Monitor shows 15.9x MB used, 10.87 App, 1.26 File cache, 1.91 Wired, and 1.94 Compressed. Swap used 0 bytes, virtual memory 20.12 GB. No noticeable hesitations attributable to compressing/uncompressing when switching windows/apps.