On every session I work on, Voxengo Span is at the end of my chain. I've created my own template which makes the curve flat for a pink noise. Since most of today's music approximate a pink noise, that's makes it very relevant. I also made the sampling time longer, which makes the curve less dynamic. It seems to be more truthful to how we experience loudness.
I think Voxengo Span is a very simple, yet effective metering plugin. Since it's free, it's an unbeatable value for the money.
I have been using Span nonstop from the moment I downloaded it. This plugin has taught me a lot about my mixing and highlighted problem areas that I couldnt hear before. The display is great. Big and Bold, (ideal for mastering) and very simple to understand. I use this plugin during tracking, mixing and mastering. I dont think I have another plugin that is used as much as span.
For a plugin that makes no noise whatsoever its helped me produce a better sounding mixes. I probably sound like an advert but no. The fact is I couldnt do without Span now.
Oh, and its completely free. What more could anyone want