That is a fine deal and Surly does still sell 9 speed but my guess is they are not going to be around a whole ton longer.

I own the Disc Trucker and haven't had any issues. If you plan on going abroad or to a place that doesn't have a shop you can always carry an extra set of pads but generally I wouldn't worry about it. There are some places on the planet that might not even have canti pads or something that will work so you would have to ship them somewhere anyway and I would still rather just have discs. I find they stop better especially in the wet and muddy, they don't wear out my rim and if I were to break a spoke or my wheel were out of true I could still brake safely. I personally wouldn't go hydraulic disc for touring but aside from that I think disc brakes are just fine.

Replacing pads isn't that hard especially if you have done it before. I don't know that it takes any more or less time than installing some rim brake pads. If it is more it won't be by much and again the benefits outweigh the time replacing pads. It is not like you are going to replace them that often unless you ride your brakes a lot.

Surly makes a solid bike and people can hem and haw about them and hate on them but no real need. Surly is a bunch of folks who love touring and having a good time, they make a decently spec'd bike for a reasonable price and are pretty easy to access. Sure their bikes are heavy and blah blah blah but their goals aren't focused on weight but durability and usability for a variety of situations. They realize most people are practical riders who are not just going to be ultralight roadies or MTB racers and some of us will want rack mounts or will want to make it a single speed or fixed gear or run wide tires or switch it all up at some point. I think they saw a lot of what people had been doing to modify old "ten speeds" and "mountain bikes" for touring and commuting and weekend fun and built a company making more versatile bikes from the get go.