I think he's definitely worth a roster spot. I have him battling for a Util position on a couple teams. He was worth having at the end of last year, so if he can come close to duplicating that, you'll be starting him soon.
He is coming back from a groin injury that kept him out about a week, and a similar problem ended his winter ball stint in the offseason. I wouldn't drop him for any of those guys, I don't expect Wells to do that much consistently to be a starter. He'd be the only consideration.
I guess it depends on your team. If he is deep on your bench and you need SP, then you grab one. Otherwise, I'd hold on to Karim for a little while.
* Steroid induced record