I love Orton, he's always been one of my favorites. He was pretty cool in Evolution and Rated RKO, but when he came out and adopted the "Viper" persona he quickly became one of my favorites.
Usually I only mark out for entertaining, talkative and funny heels -- The Rock (best work was a heel duh), Jericho, CM Punk, etc. But RKO is just so fucking bad ass and deliberately ruthless that you gotta love him. He's found a character that he can completely immerse himself in and sell perfectly. His music (I HEAR VOICES IN MY HEAD), his intimidating slow walk, his slightly psycho look in his eyes -- he's perfect.
I loved him as a heel. I loved his resentment towards HHH for kicking him out of Evolution and how he got ultimate revenge by going on a rampage against him and his family. There's few heels out there that can sell themselves as a legitimate menace like Orton can, if any. Other heels are mostly just pompous, smug and/or cowardly, but Orton would actually go out of his way to hurt you, often for no reason at all.
Lately he's been more face-like, but his character hasn't changed much. They just aren't doing much with him really. Like someone else said, there's few promos, few backstage segments, and most importantly a lack of edgy behavior. The only thing he did that was heelish the past month or so was an attempted RKO to Cena. While cool at the moment, its pretty week that thats the only heelish thing he's done.
He still has his swagger, he still has his aura, but he isn't doing stuff that Randy Orton does. The RKO I know would be jumping Swagger or Cena backstage and give them a punt to the head. The reason RKO gained a fanbase was because of his heel tactics, and they are taking that away.
This is what I hate especially about faces -- they barely have any personality. And when a character turn face he becomes just a generic good guy. Look at Edge, look at Batista and now look at Orton. I hate how WWE takes all the good parts of a character away when they turn face.
Luckily Orton isn't a complete face yet and he's still technically "tweener"... so hopefully they can turn this around. I love the idea of tweener Orton, but so far they are botching it. Make him do more heel stuff! Just make him do it against another heel. I mean come on, the crowd would go NUTS if Orton just randomly jumped Sheamus next RAW.