Rune Factory has changed the face of Harvest Moon... it'll be hard to go back to traditional HM titles after this.
Now, I've always loved the Harvest Moon series, even if the only ones I could play until now have been the SNES version and a bit of the GBA version (I seriously hate harvest sprites, as it were, so HMDS is no good). But Rune Factory is what Harvest Moon should have been all along. First of all, the game is "over" when all the main story quests are finished; that is, you've completed all the dungeons. This is piss easy. The only reason you won't finish this in a matter of hours is because about halfway through, you need to wait until Winter to continue. I reached this point in summer.
So, you do what you always do in HM; you farm. You raise livestock (which, unlike previous HM titles, you need to hunt down and tame yourself; there are four types of produce animals, and then there are worker class which water and harvest for you and battle class which fight alongside you in the dungeons, which is awesome). However, this is all secondary to the dungeon crawling in actuality, which detracts from the traditional farming simulation of the game.
Still, I found Rune Factory to be immensely fun, moreso than any HM title I've played since GBA, and I am greatly looking forward to the sequel and future titles in this newly created franchise.