We've been using this on several Macs for years now. It's so valuable that it's set to automatically start on login for all our users. If your machine starts to get into trouble with an application hogging too much memory, you will see it immediately. The window can be formed to take up a tiny sliver of space, yet still give a complete graphical view of memory usage. It is particularly good for less technical users, yet shows details useful to sophisticated users as well. There seems to be no hit on system resources whatsoever.

We've never had the first problem with this little application and the price is right - free.

It's indispensable for us.

MemoryStick (v 1.3.4, now v 1.4) works well on my iMac G5. And the v1.3.4 also worked on several other iMacs I have tried (G3, G4).
Has worked well in both Panther and Tiger 10.4.2, 10.4.3.

It is a quick and simple way to keep track of the memory and swap file usage. Usually, when number of swap files go up, responsiveness goes down.

FYI, here are the version 1.4 changes, from the help file:
"Tiger-only
Removed dependence on vm_stat
Added ability to set loudness of sounds
Removed sound options from menu
Added standard Preferences menu item keyboard shortcut"

... watch yourself.

http://www.sony.com/memorystick/

don't want to have to rename the application.

Yes, the new and improved Activity monitor can basically do what this MemoryStick does. But without the bells and whistles. Literally: MemoryStick can beep to warn you of swap-outs and additional swap files being created.

MemoryStick also places a badge on its Dock icon indicating the number of swap files.

This is tres important for some of us to know. (I've found that LiveType can go insane, filling the boot drive with dozens of swap files, so I want to KNOW when this kind of thing is occurring.)

So I leave Activity Monitor showing CPU usage and MemoryStick showing memory/swap usage.

It's Panther only.