Thanks Chris,
I went ahead and took the plunge and installed El Cap.
So far the only glitch seems to be an increase in the incidence of docked palettes
becoming "un-docked" between restarts of the computer.
I'm doing residential design, file sizes 50-200 MB, 12-14 to maybe 40 sheets probably an equal number of design layers. a small number of referenced files. I'm on an older machine, somewhat more recent video card, performance seems more or less similar to VW 2015.. I am on a fast SSD as my boot drive, that certainly helps with opening larger files.. and loading assets, obviously not with rendering or other processor bound actions. I can post more details if anything of interest pops up..