Mark Minasi gets interviewed by TechTarget in this piece on Vista SP1. Among a slew of other comments about the much maligned operating system, Mark suggests to everyone:

To make Vista "really sing," Minasi said four gigs of RAM is ideal...

He also recommends using the 64-bit OS version if your hardware can support it (which I agree as I've been running x64 for a year now). But, the upgrade to 4G is critcially important due to Vista's pre-caching in support of faster operations. This is functionality Vista does behind the scenes and is a common source of the other comment I hear a lot, "Why does it seem that Vista seems to get faster the longer I use it?"

One of the biggest anti-Vista threads I continually hear is towards the monetary cost needed in support of replacing for upgrading hardware . Poppycock! 4G of DDR2 SDRAM currently goes for as low as $100 through on-line retailers these days. And that's for the good RAM, too. Heck, I just recently purchased 4G of SORAM (laptop RAM) for slightly more than that directly off the shelves at Micro Center.

So, yes there is a hardware upgrade, but the cost is slight in comparison with the benefits.