Combat slow? Not true.
Unrewarding? I can't say that in my case, but I can imagine that gamers find combat unrewarding in Skyrim.
I never go buying or not buying a game looking at gameplay video's, but that's me

Disappointed game? Maybe many gamers, already waiting for years to buy Skyrim, are now disappointed because they espected too much ?
Or just hard to be pleased?
Okay, to be honest, I'm not so hard to be pleased with a game, especially a rpg ! I'm a rpg player by heart, not to forget I like strategy in games also (more and more).
I heart gamers who find Skyrim too easy. I play on "novice"(most easy mode) and find it still good and I make it myself more difficult because I don't boost too much and take many "perks" in reserve (kind of a "handicap" for my heroďn).
I find the combat (melee, ranged and magic!) fun to play. The same for Divinity II, but in another way give both rpg's fun with the combat.
In Skyrim I love the Alchemy system and many more of the "roleplaying" features like smithing, enchanting, cooking, sleep/rest/wait ... exploration(!), loot, trading, solving quests(some quests are repetitive, that's true!), ... and last but NOT least:
Freedom, so great !!