This is interesting considering there are only about 70 new pokes. Personally, I don't like to use any old Pokemon during my first playthrough of a game (what's the point? There's NEW pokes to try!), so I kind of miss the all-new feel of BW. That was a really great idea that did wonders for gen V, which is still my favorite gen so far (but I'm only about halfway through Y).The sheer amount of Pokemon in this game is amazing. I have never caught or wanted to use so many Pokemon in all my life.
Now, whenever I see an old poke, I just ignore it. I have no desire to catch it, unless it's one of my particular favorites (like Dunsparce), but I would never actually use one because that would mean giving up a spot in my party where a new poke could be.
All that said, I agree that I do find myself wanting to use all kinds of Pokemon, and not feeling like a party of six is enough. There may only be 70 new pokes, but they're GREAT. Easily some of the strongest designs of any gen. So I'm not complaining really, but I do wish there were more like 100.
Haven't had any problems with HMs so far as I've kept an HM slave Linoone for Cut, Strength, and Rock Smash (I know that's a TM), and both my Greninja and Heliolisk know Surf, while I gave Hawlucha Fly. In-game (which is all I care about during my first playthrough), Fly is actually a pretty good move because the AI is rarely smart enough to counter it, so I don't mind giving it to one of the main pokes in my party. Then I'm sure I'll give Waterfall to Greninja and somehow manage with whatever other HMs there happen to be.