Noo I haven't :D I thought the design for the factions Heroes V was really good since it was all thematic and such, but I didn't like how Ubisoft World-of-Warcraft-ized the artwork, everything looks cartoony.
I didn't Heroes VI that much when I learned about it. They got rid of the rare resources, I think, leaving only gold and crystal. One thing that I really liked about the old games was maintaining an economy and supply to resources that if cut would deny access to Dragons or Archangels, for example. I also didn't like the new monster designs, which I found a bit arbitrary and not "traditional" :P with things like Radiant Glories in Haven, Breeders in Inferno, and Fate Spinners for Necro. Adding the new Sanctuary faction was a bit shocking to me as well, I don't find it to be fitting with the original factions. They seem really MMORPG-ey, kind of like adding Pandas to WOW. So my impression of it is pretty poor.
I enjoyed Heroes III immensely though, I just found the game really well designed aesthetically. I've never finished a campaign myself, but going through different maps is pretty fun. My experience is deeply rooted in Heroes III though, and so there are gameplay features in IV that I'm averse to like simultaneous retaliations. Also, I found IV to be a bit ugly XP Maybe I'll try it out, if only to play a wholly different game altogether. The unicorns have rainbow manes and I don't know if that's a good thing XD
I haven't tried In the Wake of Gods :P I've never played multiplayer either, but the game is fun enough on its own.