I have a 12" iBook G4@800 with 640 MB RAM running 10.4.2, with a 60 GB 4200 PRM HD and an iTunes Library occupying 36.2 GB. If you have a Mac with more than enough RAM and large, fast HDs, the following post may not do very much for you. In Panther whenever someone started to report slowdowns the standard recommendation was to clean up their HD and free up some space. About 4-5 GB free space was a bare minimum to let the Mac run well. This usually did the trick. After upgrading to Tiger (A&I) I cleaned up a bit and was amazed with Tigers initial responsiveness, which was a step up from Panther, but right from the start I started getting more than the occasional beach-ball which brings about those "painful" slowdowns. This even if I had more than 5 GB free HD. But one thing I noticed was that Tiger seems to "eat" HD space while running, so that after a few hours I was down in between 4 and 5 GB free HD space, i.e. into Panther's danger zone. It was time to check out what's really going on. My Activity monitor reports that the VM (virtual memory) typically needs well over 5 GB (!) in typical use: iTunes/AirTunes, Safari with a couple of tabs, Mail, XRG, Meteorologist, Quicksilver, MainMenu and - the one of the real bad boys - Dashboard. AM reports ~3.5 GB VM before running Dashboard for the first time after a reboot, and ~5 after all my Widgets had been fired up . No wonder the poor iBook's struggling, when VM wants to use 5 GB and the HD just has about 4.5 GB free space. Quite embarrassed that I didn't connect the Panther advise with initial reports of Tiger needing more RAM (and thus also virtual memory) earlier I started cleaning up my Mac manually, i.e. threw out all non-essential docs and apps (after burning them to a DVD, of course) and deleted some obvious duplicates from iTunes. Then I used MainMenu to clear out caches and logs. After this cleanup I had ~8 GB free space. To decrease RAM usage I ditched (more than) a couple of Widgets. Widgets also not only takes up quite a bit of real memory, and reducing the number of active Widgets helps quite well in reducing the number of pageouts, which leads to beach-balling, a pain on a 4200 RPM disk. I also went into iTunes preferences and set the streaming buffer size to small, which actually decreases the amount of HD space Tiger "eats" when in use (I think I'm on to something here ). Now using the iBook is a fantastic, in typical use, with RAM hogs like iTunes with AirTunes and Safari running along side Mail, TextWrangler and the above mentioned enhancers, with only active 6 Dashboard widgets, Activity Monitor reports a VM size of "only" ~4.5 GB, well below my just under 8 GB free HD space (after a bit of runtime). It's like getting a new machine, applications open in a fraction of the time it used to. Even when fireing up something like Photoshop it's maintaining the responsiveness. The number of pageout has also decreased, and now mostly occurs whenever iTunes changes tracks (I'm using crossfade playback which actually is very resource intensive, no wonder they haven't implemented this on the iPods, it would be a real strain on the batteries) or whenever I have more than 10 apps running. A funny side effect is that the CPU is actually running hotter now, presumably because doesn't have to wait for pageouts all the time... To summarize: Tiger can run very well on a 800 MHz G4 with "only" 640 MB RAM (just over the 512 that many claim is the "bare minimum") on a measly 4200 RPM HD. You just have to keep enough free HD space available and get rid of as many Dashboard widgets as possible to reduce both real and virtual RAM usage.