Here's my DIY compressor cabinet I built back in May, 2012 and still holding up fine. If you'd like more details let me know.
How about a BOM (Bill of Materials) and a write up on how you built it? Or a link to it if it's on here somewhere?
Is there a screen over the fan on the bottom?
Looks good!!!
Have you ever had snow get high enough to cause air flow problems thru the cabinet in the winter?