Yes. It's worth at least $20.
And I disagree. The stealth gameplay is good, but if you play on the highest difficulty and go around killing everything, it can be quite challenging and fun. You die in like 3-4 hits, the enemy dodges your attacks, they even counter sometimes, they surround you, etc. Basically, if you fight against 2-3+ enemies, you will get owned, and I love that. You mix up magic into the combat and you are able to take more enemies, but you can still die very quickly if you fuck up.
My first playthrough was completely stealthy, but I shit you not, I enjoyed the second full-combat one a lot, too, maybe even more. You also get different things happening depending on whether you kill a lot or not.
I plan on playing a full combat one again later, because the sheer amount of combinations you can do in a battle can make for some awesome crazy shit. I'm amazed by this because the game has ZERO combos, you just mix up a lot of abilities. For a game that wasn't all that focused on its combat, it did a hell of a job with it.