I still think polini is the best kit for puch. They rip hard, both low, mid and top end (elliots does like 65), and they are proven. There are some sick gila's out there, but from what I've seen, they are about as fast as the fastest polini's when paired with a 24 mikuni and simonini. Price wise, gila is cheaper, but now discontinued, or so they say...
So yea, if you want a puch kit, polini is the best.
I think people are warning against the 2 (metra/gila) as first kits because it will be difficult to get the most out of it, and if you haven't messed with all the variables before, chances are it will break. I started with a polini and rode it very hard, then had some problems. I've taken a step back and am working with 50cc now to gain even better understanding of how everything works, then once I'm doing 50 on 50cc I'll return to the larger kitted realm. I think too many people kit their bikes too soon. They aren't built to do 50+, so you need to make sure its solid and not going to blow up on you.
Most people warning about blowing up the kit are probably doing so because they've done it themselves and are trying to help you save some time, money and frustration. Seizing your new $500 setup sucks pretty bad.