There are a number of companies that have used this technique to push capacitors to the limit for high frequencies, and mids, especially when they are planar. Infinity used the technology in their last speaker the Epsilon. JBL was in the forefront with their Everest DD66000 amongst other models. Other manufacturers have implemented this technique as well.
The biggest issue is that if you are using high end capacitors to begin with - you end up quadrupling the cost of the network to add the charge bias to the network. So you don't see it a lot unless the speaker is very high priced.
Then there are those that think it's black magic. There is actual science behind the technology. And for me, if we are going to the problem of capacitor microphonics, the type of solder, signal paths, variable gauges of wire etc. - all of which are measurable and laughed at years ago - then why not take this technique seriously.
JBL went over the top with full 24db/octave passive crossovers. Now THAT is expensive and complicated. 6db is pretty much useless especially in a 3 or more way system - never mind the driver overlap, loss of image and potential clarity. And when it comes to 12db/oct - just kill me.
At any rate, I've attached a schematic of the tweeter section form the DD66000 for your curiosity. Pretty elegant. Mind you in those days they were still dealing with poly caps and monster cable. As I develop the Signature version of Alex - guess what I'm working on ...