@Bruno Many thanks for answering my question.
@Washburn Thanks for your replies. I'm assuming you thought I was simply attacking Arturia. Considering the strange behaviour that occurs on synth forums I can see why you may have thought that. I haven't been around on here for quite a long time, but my previous posting history should show I've been quite supportive to the Arturia community at times, though I don't hesitate to call a spade a spade when necessary.
I agree that demos aren't necessarily a good representation of what a synth can do, but on the other hand the point of a demo is to give some kind of demonstration. Agreed, it won't substitute for actually testing a synth, but it should give some indication of what the instrument can sound like, and indicate things to try when testing it hands-on.
I never entirely write off an instrument until I've tried it myself, but if every time I hear it I don't like what I hear, it does tend to push it further down my priority list. To be honest, the only reason I'm still checking out these demos at all is because I have a certain confidence in Arturia, and also I expect a designer who's worked on filters for Synton and therefore presumably worked with Felix Visser isn't likely to produce a filter that pops and squawks much of the time unless it's pushed into it.
I do intend to try the MiniBrute if I encounter one, but in the meantime I'm glad I've had my question answered, because now at least I can suggest to people that they reduce the signal level going into the filter, which is more constructive and more beneficial for Arturia than my previous answer, which would have been that the synth has never sounded good to me in any of the demos I've heard, and that impression may well have been reinforced by the unfortunate person trying it without being forewarned about the levels.
I'm not likely to buy a MiniBrute myself, at least at present, partly through lack of money but mainly because I already have a good range of analogue synths. But people frequently ask me about budget priced synths, and I'd rather have a positive and correct views of the MiniBrute than a partial one based on hearing virtually everybody pushing it till it screams. At least now, if someone says they wondered about the MiniBrute but it always sounds screechy and distorted, I can suggest they give it a second chance.