I have a feeling that superior drummer may not be worth the investment.
I use Ez for very quickly creating drum beats. It really is so simple which I love then you can go back and add fills or manually edit drums after.
I know that you can split each drum beat into it's own track, convert them to audio, add compression or play with EQ etc so there is loads to do with this before you need to look further.
I would imagine that superior drummer is for those looking to spend a lot of time on their drums to get them sounding as real as possible for professional tracks. To my ear, what you can get with EZ does this already for my needs!
If you do decide to get it I would be very interested to hear your reviews on how it compares.
Instructor - Ez drummer is the best thing I found. I have an alesis SR-16 which I tried to use but never got on with it. I used beta monkey loops which are great sounding but restrictive. Then I found Ezdrummer and i really like how easy it is to use and how simple it is to get a decent drum beat going - all full editable at a later date.
Like Don says, using it alongside something like Cubase makes it even more versatile as you can build you whole song up using different lops and fills and easily zoom in to edit any parts. This can be done before or after you have laid the song down.
As you will probably have guessed from my limited recordings, I start off with a loop which I repeat as many times as I want. I can then go back in after and add fills or change the loop slightly for different parts of the song!