I've used SysMetrix for a few years.  It's pretty customizable and skinnable, and although it tends to eat resources (depending on customization and skinning), it's mostly met my needs.  The one issue I have with it is this:  it doesn't give accurate memory readings (physical, swap and virtual cap at 2 GB).  Using SysInternals' Process Explorer, I can verify memory readings, but would rather not have to resort to yet another program to get one bit of info (however important).

I recently tried Rainmeter and, although it isn't currently supported, it does a lot of what SysMetrix does for me, using about the same resources.  What's more, it gives accurate memory readings.  The way I figure it, I have four options:

1.  Stick with SysMetrix and live with the memory issue
2.  Switch to Rainmeter, even though its support is nonexistent
3.  Use both, and take the resources hit
4.  Find another solution

I appreciate any input all of you might have.