Wayne, same with me but on W7 64bit. I have 16GB of memory, no swap space and LR never went over 8GB. I use a core i5 on Ivy Bridge MB, the area where i suspect most of the performance of LR is determined is the CPU time, which could point to programming issues or to performance hinders with the SQLITE database. The system disk and the catalog disk both are Samsung 830 SSD's, not noted for being slow actually, noe of both are more than 50% full. LR does write temp files to the systemdisk, but from my interpretation of the resource monitoring of LR it is centered around the CPU processing mostly, so code or database.
My Win7 system is exactly the same except the LR images and catalog are on at fast Western Digital hard drive (OS and programs are on a SSD). Quite frankly I've never seen any issues with LR at all here. We are off to Croatia in a couple of weeks and I anticipate having 3-4 CF cards full of images. I haven't had this many to download on the current system so it will be interesting to see how the performance goes. I did invest in a new USB 3.0 card reader.