One thing about filming planes fly is that you can more easily predict the next frame of the flight. Sweeping steadily across the sky, with some practice and a few cool tools, you can pretty much keep the viewer from needing dramamine when they watch your video. With Heli's, well, not so much, especially flying 3D. Unless you know the habits and pattern of the pilot filming can be quite an exercise if you want some close up images. In fact, most of the video i see of heli's are filmed at a good distance.
With my pocket camera (that takes HD video) and armed with a manfrotto monosteady, I attempted to get as close up to my buddy's heli in flight as i could without feeling like throwing up when i reviewed the footage. It ended up pretty challenging as i stumbled at first to keep it centered. To boot, it was like 120 degrees and my sweat felt like it was boiling my flesh.
Got the footage cut and edited to a pretty watchable video. Here's the link: