Vista is just like any previous version of Windows...at some point it went to market with their best effort to date!
Microsoft did a bangup job with Vista, but there's ALWAYS room for improvement, especially when ingenious hackers have too much time on their hands.
Enter the patches. Patches are a valuable and necessary means of upgrading key system components for security and performance purposes, as well as rolling out new features that you'd have to wait 4 years for otherwise. The developement cycle that Microsoft uses is 4 years between releases. That's a long time to wait for a patch that fixes a security hole that hackers are taking advantage of.
As to the memory usage, in most cases it will be negligable. The patch usually replaces an existing piece of code.
Bottom line, apply all patches unless you have a specific reason not to add a particular patch. (only saw this once where we needed to keep a very old version of Java working to interact with 15 year old equipment...but only once).
Michael @ IronOakIT, Calgary, AB
http://www.ironoakit.com