Overall, the mood and emotion of the music changes alot, sometimes slow, sometimes fast and harder sounding, which isn't bad but... it does kind of weaken the entire song overall (although individually I like both parts [the quieter sections and the harder section]).
Overall, very true to the original, a good job turning that little sound clip into a four minute long piece. I would have rather seen the entire song sound like the ending (which is more "rocking" I guess). The title is misleading, as bowser doesn't sound THAT angry until the ending of the song.
Still though, worth the download if you like SMB.