IIRC, the problem was, both drivers and applications were rarely made to support PAE, so it went almost entirely unused, outside of servers (where the hardware and driver quality is generally better, and so was worth enabling).
Even so, a flat 4 gigs is a flat 4 gigs, so to use that much in an application, you have to resort to the ancient Intel tradition of segmented memory (or since we're talking protected mode, technically, "selector"), which so it seems, no one has ever liked, at any time, in history.
Which is funny because they had the identical problem in the late 70s (migrating from 8 to 16 bit CPUs, like 8080 and Z80 with flat 64k addressing, to 8086's 1MB), and this was their solution (segmentation).
Tim