Do M13s have any quality or reliability problems I should keep an eye on?
Possibly...check this:
https://wiki.geekhack.org/index.php?title=IBM_M13_Y-Cable_PS/2_Family"The M13 controller produces a great deal more heat than a standard Model M controller. The reason for this is that the M13 controller is actually comprised of a total of three controllers; the matrix controller for the keyboard, the TrackPoint II controller, logic and translator for the TrackPoint, and the PS/2 passthrough controller segment. All production M13 controllers are covered by a metalized cardboard heat shield. While removal of the heat shield is unlikely to damage the controller itself, it will damage the lower chassis, which is M13 unique.
Repairs to the M13 controller should only be performed by people with extensive soldering experience. Replacement parts cannot be sourced for the TrackPoint elements. Common problems with M13 controllers include capacitor aging, cable damage requiring cable replacement, and worn matrix contacts."
Also I know that the plastic of the top case is thinner than usual (at least in certain places) to accommodate the unique controller of this board and so is a bit more prone to damage from abuse such as blunt force trauma.
