Just a quick addendum.
With 3.1, I had to do a kernel re-compile to use ISDN (ISDN in the UK is a bit of a PITA to obtain, never mind set up here in the UK). Is there any built-in ISDN support in 4.0, or does another "make dep && make clean && make bzImage && make modules && make modules_install && cp arch/i386/boot/* /boot" loom on the horizon?
Dave