Mixed reviews? Hmmmmm... anyone who denies they're great pipes is either in the dark or jealous. The build quality is second to nobody, the materials are top shelf, the design and racing experience can't be argued, and they sound like sex. The only pipe I've seen up close that truly rivals the Akrapovic for fit and finish is an Arata, but I'm not big on how many joints the Arata uses. I'm biased, but I won't own anything else.
BUT... they are DEFINITELY one of the most expensive pipes available. I agree with many people too that for some the extra money could be better spent going into suspension or other mods and a cheaper exhaust. There's other pipes on the market that cost less (Yosh, Laser, Arata) and are still fantastic pipes. Everybody is different, and that's good, because I'd HATE to see EVERY Kawi going by me with an Akrapovic on it.