I guess I'll contribute a bit, being that I've referenced this website once in a while during some of my previous projects. I work heavy line maintenance on commuter aircraft. Alot of the guys herein my hangar have these Harbor Freight boxes and they work beautifully for what we do, they're just about the right size, easy to modify, and cheap enough to not worry about spilling hydraulic fluid on it and ruining the finish. My box served me well for about 2 years. The pneumatic lid holders help up well and I had no issues with the drawers. The locks these boxes come with are pure trash though which led to one of my first and most convenient mods.
I added a bit of aluminum here and there to line areas of the box top so I can use it was workspace and not worry about spilling acetone or hydraulic fluid. Adding a pad lock to this box was one of the biggest convenience mods and made me love how easy it was to have access to my tools and leave my keys on my box secured. I also closed up the sides and added snap latches to the front bottom flap door to keep guys from "borrowing" paper rolls, buckets, etc. It worked out great. Hope this helps someone else with any ideas they might have.
These boxes are well worth the money, even for someone who can afford Snap On and Matco, I'd still pick this HF box over them just due to bang for your buck.