I'm in the planning/collecting stage of some fairly inconsequential part swaps on my Platypus.
V-brakes -> Cantis: For over 10 years I've had a set of Paul Touring Cantis on an old Univega Alpina MTB, which has some non-standard (or extinct standard) brake posts with the pin holes outboard of the posts. Since you can't really find brakes for this configuration any more the simplest solution is a brake that doesn't use the pin holes (the brake tension spring is internal) and that's where the Pauls came in. Last year I realized that Diacompe 988 cantis use a similar tensioning mechanism and can be had for $30 a wheel, and now have finally swapped them on to the Univega (they work great) freeing up the Pauls for the Platypus. Just waiting on brake cable hangers and deciding on levers.
The Diacompe MX2 v-brakes being replaced are great brakes, so apart from getting some Paul parts on the Platypus this change is really about the rack.
Mark's Rack -> Nitto 32f: I've had no issues with the double strutted Mark's Rack but the combination of a good deal on a 32f, the thought of switching the Platy to cantis, and a possible use for the Mark's Rack on another bike brought this one about. It'll go on with the Touring Cantis.
-Dave (suffering from summer "bike brain")