As for system performance, mimalloc's effect isn't particularly noticeable in regular use. Or maybe I just don't stress the allocator often enough. There may be more daemons running by default, but they are also activated on demand if you aren't using them, so YMMV on that.

For desktop use, it feels like an early (but already quite usable) version of what a respectable systemd replacement would look like, and I think that's its greatest strength in practice.