It's not that much bigger and has a number of similarities to SDC. I wasn't as impressed as I expected to be when I went a couple years ago. It was probably because I went in expecting a bigger SDC though. It is certainly it's own park, and it has a much less cohesive and thematic feel than SDC.
The old SDC Tennesee sections are really nice, and I enjoy the Dolly Parton museum and some of her areas of the park near the front, but the newer back areas leave a lot to be desired. Wild Eagle has no theming and a very uninspired layout. The whole wilderness pass area had a SF feel with very light, slightly cartoonish theme. Timber canyon or whatever it's called with Thunderhead and Mystery Mine looks a lot better, but it's packed with rides and not much else. Mystery Mine is the big exception to everything that I have always been jealous of. That is possibly the most thematic ride outside of a Disney park, and it was my hope at the time that it would kick off a new generation of highly themed HFE rides... but then they built Wild Eagle.
But overall though, the rides are nice and there are a few interesting shows and non-ride things to do. The old section of the park is actually really nice and has a great SDC feeling to it with several shops and craftsmen. I haven't done Lightning Rod yet, but hope to get out there next year. That ride is supposed to be even better than Outlaw Run.