As for my feelings - I like most of them, even though the departure from the original style is quite significant and...
- Blood Mage looks a bit wimpy - I know he's a mage and a Blood Elf, so he can't really be all that bulky, but in the original game he seemed "bigger", maybe because of the cape being wider.
- Achmage - the horse is cool, but I'm really not sold on the mage... I mean, for an Archmage his robes are very plain and his shoulders look rather low quality.
- Paladin - military haircut... ugh.
- Flying Machine - upon closer inspection, I agree with
@deepstrasz that it's a bit too steampunk-y.
The rest of the human units are fine with me. I really like the Dwarves - Mountain King is the best looking hero for me (I agree it's very different from the original - I just like the new look more) and I absolutely love the Rifleman, the Mortar Team and the Gryphon Rider.
- Blademaster - I think that shoulder pad is a bit excessive considering the Blademaster was supposed to be this fast, agile, stealthy warrior and those don't usually carry too much armor.
- Farseer - I'm not a huge fan of his cape. If you zoom in, it looks okay, but from the distance it made me feel like his head was bugged.
Suprisingly, I really like the rest. My favourite hero is the Tauren Chieftan and as for units, I think the Demolisher looks absolutely amazing. The Tauren, Shaman and Witch Doctor are also really great.