My first HDR with the Rebel T2i. Photomatix doesn't recognize the T2i RAWs yet so I'm not sure if this could've been better. The sky looks funny.
Camera: Canon EOS REBEL T2i
Aperture: f/22.0
Focal Length: 21 mm
ISO Speed: 3200
Nice work. Photomatix recommends you process your RAWs prior to merging anyway.
http://www.hdrsoft.com/support/faq_photomatix.html#tips
For the sky, you could add one of the original bracketed shots as a layer in PS and mask out all but the sky. StuckInCustoms has a great tutorial: http://www.stuckincustoms.com/hdr-tutorial/
...or just crank up the Highlights Smoothness in Photomatix.