Sorry to bring an old thread back from the dead..but..
Often the complaint with aluminum is that it's s stiff ride, not quite as comfortable as steel. Personally, I prefer my aluminum frame ( Marin Novato ) but have been considering purchasing a steel touring bike. As I'm getting married this fall, and $$ is limited I'll probably just end up using the Marin for this season. To help with comfort and road vibrations I'm thinking adding a carbon seat post and handle bar might solve the problem? Perhaps also adding a caarbon front fork? Oddly enough, my Marin has all the braze on for touring (front fork & rear braze ons), even though it's a "urban ride".
The only think I don't like about the bike is the frame may be a bit too small ( I'm 6'1" - frame 18.5" ). I think the small frame cause my muscle an exacerbated my knee problem last tour.