The Miura 20 is a solid, versatile, built for hard use and easy on the eyes backpack. I also own the discontinued RT25 and I have put that bag through the gauntlet. I bought the M20 to serve as a replacement, if only because my RT looks a little rugged (though I still use it to full capacity). And while it's not exactly a 'next gen' RT, it is obviously from the same train of thought.
pro; If you have an Arc'teryx backpack then you know the quality of make and unique styling. Roll top is crucial. (why don't you see more of these?) Both outside pockets are Tardis-like, open the zipper and the cramming space is vast. The jury is still out on the metal accessory-strap-fastener things but they will never break. Gone is the molded foam back in favor of more breathable fabric combination and in fact a more contoured shape. Main pocket is substantial enough for a weekends worth of clothes and cameras and books and so on, and is lined for hang up free packing.
con; Those two zippers on the sides (completely opening the main compartment) are cool, and burly, but just not necessary. One of the things I really like about the RT is that it's a big sack. Those two zippers really just increase the likelihood that you'll accidentally yard sale your gear in the airport or bar (keep 'em buttoned!) And there's another, even more useless zipper on the inside of the main compartment accessing the vertical outside pocket, but not a two way zipper. Inside going out. huh? I have absolutely no idea what it's for. Really, I'm baffled.
In summation, if you're looking for your next RT the M20 is kind of that. Though, where the RT looked a little foot-soldier-of-the-future, the M20 is totally bring-your-yoga-clothes-to-the-office or best-dressed-at-the-weekend-war.