The most important spec to consult is the wireless chipset. Dell tends to favor Broadcom.
Any distro, such as Slackware, that does not do Broadcom automatically will require some extra work. Distros that include Broadcom support, such as Ubuntu, do splendidly out-of-box.
Other than that, I have never had an issue with Linux on any Dell, and I've had three desktops, two laptops, and one netbook running Ubuntu, Debian, and Slackware.