Jim,
Here's a link to a memory module review that gives a brief explanation of the different memory parameters and a link to more in depth information (I didn't read the latter).
http://www.techwatch.com.au/reviews/hardware/mushkin_pc150_hsdram/
Hard_warE,
Here's a link to a reputable US site that sells VC memory:
http://www.memman.com/
I read an article (don't remember where) a while back that compared VC memory to some good SDRAM. All I remember is that the reviewer ultimately got better performance out of SDRAM. (Maybe a higher FSB?) I don't know how accurate this is.
Mike