Fedora, and other distros install a PAE kernel if the hardware supports it.
Are there any negative effect on running a PAE kernel on a machine with less than 3-4Gb ram ?
Ubuntu 9.10 benchmarks including 32-bit and 32-bit PAE kernels:
"...we did not find using Ubuntu's 32-bit PAE kernel to have a dramatic performance impact whether it be positive or negative"
The conclusion is probably the same for Fedora.
Stability doesn't seem to be a real issue.