Ha! It took me forever to get that one achievement, when you have to speak with every soldier in Colony 9. I've probably completed around 200 sidequests, so far. The next time I play, I'm returning to Colony 9, Tephra Cave, Colony 6 and the Satorl Marsh. I'm going to do a good sweep at night and daytime, so I can locate any new sidequests. Then I'll be on my way to the Eyrth Sea, right after I check for any last sidequests in Frontier Village. I've collected so much awesome shit from doing so many sidequests, not to even mention the amount of money I've accumulated. But don't worry Rory, I'll finish the game at some point. I don't have Xenoblade Chronicle's fan art in my signature for nothing you know. ;)
Rory, have you seen anything about, "The Last Story," package deal? All launch copies will come with a music CD and an artbook. If I had the money, I'd pre-order a copy just for the music CD and the artbook.
By the way X-145, there's a secret area in Teprha Cave. Which you can only gain access to, by completing certain sidequests later in the game.