I don't think I can answer that. Depends on the bike and on the rider's preference. I commute on my cx bike, with cx tires and with road tires, and it's OK with me, but I think it's pretty individual (and does differ from bike to bike).
Good luck!
Have you told your LBS what your plans are for future bike purchases? Given the amount of money you're likely to spend in the future, I'd think a shop owner would go out of their way to help you find a cross bike that works for you, in the hopes of getting your repeat business on the other stuff you mentioned. At least, that's what my favorite LBS would do.
RE: commuting on aluminum - my first road bike was aluminum and I used it as a commuter. I then upgraded to carbon, and sold the aluminum. But, when I bought my cross bike, I got a Redline Conquest Pro in aluminum and it makes for a great commuter!
Good luck finding a cross bike that fits! Careful, cross is addicting!
I agree with Liza on the steel vs. aluminum comments. I race 'cross A LOT, and do it on an aluminum frame (actually two of them). You would have to have a VERY SERIOUS crash to break an aluminum frame, and with the amount of carrying involved, it is MUCH lighter than the steel alternative (I am actually thinking about moving to carbon...).
Like others, my first road bikes were aluminum, and I loved them (till I discovered carbon). That said, my winter commuter is my old aluminum cross bike, and I put A LOT of road miles on it very comfortably.
SheFly
"Well behaved women rarely make history." including me!
http://twoadventures.blogspot.com
well...i'm pretty sure the ONLY frames that'll fit me are Bianchi and MAYBE Pinarello. so i'll probably end up with aluminum or carbon. the pinarello looks sorta nice...so does the bianchi...
i'll have to see what i have to do in order to get my LBS's to order the smallest size without me buying it first...
I don't have my inseam measurements on hand, but I'm only 5'1" (on a good day!) and I very comfortably race on a Surly Cross-Check. I have a long torso too, so presumably there's not much left in my inseam
Is there a local bike club around where maybe you could find a used cross bike to buy or test ride? That way you won't be making such an investment on equipment before you've gotten to try out the sport! (I mean, I'm sure you'll love cross because it's awesome, but there's a lot of great used bikes out there for cheap!)