Swap files vs. swap partitions —
It took far too long to find this half-remembered linux-kernel thread on Google amidst all the results (mostly from distro installer guides) claiming that swap partitions are preferable to swap files. Here’s hoping the link below will help future searchers.
In 2.6 [swap files and swap partitions] have the same reliability and they will have the same performance unless the swapfile is badly fragmented.
— Andrew Morton, on linux-kernel.
(There is a performance difference under Linux 2.4, though, as explained at the link above.)
Update: Tim comments that swsusp (the kernel software suspend-to-disk support) only works with swap partitions, so there is still one good reason to use a swap partition. Suspend2 doesn’t have this limitation.