Honestly - nothing really. I've spent chunks of time doing tutorials & playing around only to realize I don't actually have a need for it in my workflow. I do CAD and rendering & stuff in other packages already so the time investment to get proficient at Blender just doesn't seem worthwhile right now, especially when there's other specific apps where my time would benefit me a lot more.
If I was doing more freeform kinda creative stuff I'd jump into blender right now. But...mostly I just love the idea of blender. I've enjoyed the few times I've needed to do something quick and been able to use it. And I really enjoy watching people use software and cg breakdowns etc. so Blender stuff is like digital porn for me when I just wanna kick back for a few minutes.
Dunno, I'm doing a bit more animation lately and am starting to hit a wall with my current software so I'll see what the next few months brings. But ja - busy learning other software that's more beneficial right now so need a good reason to properly jump into Blender. Priorities I guess.
You using Blender at all? You do architectural visualizations sometimes right?