I have to say I'm rather enjoying this series as I get to know the characters. The vast majority of knocks on this series are really unfounded. The acting is really no more awful than the original was. The special effects are as good, if not better.
As to stealing from other show's well the original did their fair share of that too. From I Dream of Jeannie, to Bewitched, Harry Potter, and even Snow White, The Sword in the Stone, and The Little Mermaid. So far at least the demons in the new series actually look demonic. A knock of mine in the original series. Not to mention the number of evil underworld females, all buxom and beautiful, showing maximum cleavage in the original.
The original had more than it's share of flaws in acting, story lines, and special effects. But it was quite entertaining. That's the bottom line. The new version doesn't have horrible acting, horrible special effects, or a horrible story line. In some respects it's better than the original, in others it's on a similar level. It certainly has room and potential to grow. Most importantly, it is entertaining.
The truth is if you can simply let the original go and approach this as a new series about three new witches you'll probably enjoy it. If your' so connected to the original that the only thing that would make you happy is a continuation of that show you likely won't. But when you go in with a negative attitude in all likelyhood you're just going to look for reasons to hate the new show.