Nice image. Brilliant location. Composition is good, and you've done well with the HDR processing, however, the bottom left (the trees) is still too dark, and the haloing at the top of the rollercoaster on the right is an unfortunate by product of HDR which I'd try to avoid (I know it's easier said than done). Also, the colours in the sky look a tad flat... a result of noise reduction perhaps...
All that said... this is a good shot, and a worthy addition to your profile page.
The green/trees seem a bit darker (maybe it's my monitor). I like the "buried" part of the rollercoster in the woods. Nice also you got the kart on the top.
the blue struts are abit to blue. I like the composition. Personally though I'd crop it a bit less high in the hope of getting a bit more detail in the roller coaster bugies. I like the way you've capture the ups and downs in the coaster and the colours are lovely (apart from the blue).
Fairly sure this is not a multiple exposure HDR, (Set up a tripod in the car and stopped it at the top of the climb?) but the effect works well, regardless of how it was accomplished.