We mix and match because that's the way to get the ultimate touring group. I don't have too many bikes that are a single group, i.e. all Ultregra or all Sram, for good reason. Some parts from some groups do a better job than other parts. Just about any high end Shimano triple front derailer vs any mid to lower end Shimano triple front derailer comes to mind. The Ultregra front is narrow and difficult to set up for a wide range cassette. The Tiagra, on the other hand, has wide plates, isn't too sculpted and is more forgiving for a wider range of gears on the rear cassette. It just does a better job. Same holds true for all Shimano front derailers. The XTR is a nightmare to set up properly but the Deore is simple.

Sram mountain fronts are completely different and work wonderfully, no matter what level they are.

For hubs, I'd go completely outside the big manufacturers. I'd choose, in increasing order: Velocity, Velo Orange, White Industries, Phil Wood. The White Industries and the Phil Woods are almost neck and neck. The Whites roll a bit smoother, are less expensive and are a lighter but the Phils can be taken apart with a 5mm wrench. The edge, for me, goes to the Phils.

For cranks, I'm not sure where to turn today. Shimano has the edge when it comes to installation but they have been going all goofy with gearing lately. A Shimano Deore trekking crank with a 48 tooth outer ring would be ideal but they don't seem to like to make them for the American market. The only Deore I can find now comes stock with a 42 tooth outer which is woefully inadequate for road riding, unless you want to spend all your time coasting down hills. Raceface is okay for cranks but, again, the gearing is wrong for road riding and the installation isn't as simple as Shimano.

Brakes: For cantilever, I'd take Pauls. If I had to use discs, Avid mechanicals.

Overall, I pick components that work well and are durable rather than components that "match". They have to work together but they don't have to have the same logo.