Envelope filters are kind of a niche in the pedal market, and as such they tend to be on the pricier side. This pedal sounds really good at a price bracket in which there's few other options. That alone is worth the price of admission. I have played the mooer envelope filter, and it's good but noy as good as this in my opinion. I've also played digital envelope filters from Helix (Hx Stomp), Boss (Katana mkii) and Valeton (GP-200). Of those (and this includes the mooer) I'd say the best one is the Helix. The B-Tron is better than that.
How do I define "better"? The responsivness to your touch dynamics, how it opens up and closes and the clarity of the sweep for that unmistakable 70's sound. It's a joy to use once dialed in.
Now on to the cons:
Sound is the only aspect in which this pedal truly shines. Learning to dial it in is a total pain. I have since learnt that this is mostly true of all envelope filters, and that they're finicky effects in general, so don't judge the B-tron too harshly for it, but be forewarned. It takes time to find "the sound" and it's very guitar dependant. It also pretty much needs to be first in your signal chain.
The build quality is just fine. Sturdy metal chassis, yes, but knobs which feel flimsy and prone to breakage. Mine hasn't broken yet, after living for months on my pedalboard, going to rehersals and such. But I try to treat it delicately.
Extremely loud button press. It's a very audible pop whenever I step on it. I am considering looking into whether I can mod the switch to get rid of that.
Finally, size. It's just ridiculous. Behringer obviously wanted to recreate the look and feel of the original Mutron, and admittedly the pedal looks beautiful. However it's too large to justify, and it won't fit on a busy pedalboard. I can get away with it because I only use 7 pedals.
To sum up, if you can live with these cons, it does sound great. If these are a deal breaker, look at something more expensive, or compromise on sound quality with the mooer or some other inexpensive option. Or go digital