I doubt its important at all, because they are implementing things directly into the sound engine; this completely changes the implementation and it is being done by knowledgeable people outside the bounds of SQF. I'm sure he can specify the features he was trying to poorly implement, and they will do it correctly (The internal sound engine they use, per the leaked source, is perfectly capable of many of these things such as echo, distance reverb, filtering, etc).
Why do people like it? The same reason they like TFR - It was first out, so it got picked up, and that leaves it very entrenched.
JSRS fits the more "gamey" aspect the majority of new A3 players desire; the simulation players of A3 are a minority these days. It may not sound realistic, and may have bugs, but it sounds better than vanilla.. I might throw in something about youtube too; people watch videos and think its real (like blastcore) - not realizing that they are the videos he sampled the sounds from, most of the time. (Or in blastcores case, people dont understand tracers look like that because its a video).
My biggest concern would be the fact *they dont care about big games*. They have officially stated that they are focusing on BF-style servers and gameplay; e.g. ~30 player TVT scenarios. This is their bread and butter they want to focus on from a design perspective, so not like it much matters if it was fucked anyways.
Do larger communities use it? No, they don't. How can I speak to this? I'm in a few skype channels with most of them. The few communities that allow optional mods, the admins hate it. There are 2 communities which in fact *do* use JSRS, and their technical people also complain about it up and down all day, every day.