- We need magnitude zooming. The slider on the left should change the sensitivity of the amplitude axis. If turned all the way up, the graph would display a range of 0dB to -40dB, if turned all the way down, it would display 0dB to -100dB. Right now the graph appears too "flat", even if a signal (such as a snare) actually has significant peaks.
- At slow refresh rates, the graph jumps between seemingly random snapshots of time that don't really tell a lot about the signal. At fast refresh rates, it moves so fast that it's very hard to read. The "peak hold" curve is much smoother and better; I usually just look at that, but it's quite hard to read because of the colour...maybe there is a way to make the normal curve behave a little smoother?
Again, this is a very great plugin already and it's generous to give it away for free!
If you can fix these points, I'll be happy to make a donation. 
