The 1.5 rule is very old, and I actually ignored it. The reason is that up to (and including) XP, the OS seemed to favor cache as opposed to background apps. I think ever since 64MB RAM in 95, I always disabled paging file. And now I'm using 8GB in Windows. I even limited my laptop to use only 4GB out of 8, but that is due to hibernation file, rather than page file.
PS: just in case you are wondering, my laptop came with 1 4GB stick, and I bought one more for dual-channel...so that combined with hibernate file made me decide to limit to 4GB.