The Bose L1 does has some advantages over other PA systems. I'm not going as far to say it's the best PA system, but the product itself definitely has place in the market. PA speakers in general aren't typically very accurate and I could see how the L1 would fit in a jazz environment. They certainly don't sound bad, and they aren't piercing like some PA systems can be. They fit the mold for Pat Methany because extreme high output is not necessary, compact size helps as well as setup, and they have a mellower sound than most PA systems.
At $999.99 the price is a little high, however I'm not aware of a product that is quite like it. I imagine the appeal of such a system is quite high when the prospect of tearing it down and putting it up show after show makes the L1 a candidate for those that can afford to purchase them.
The product itself is not bad. It is unfortunate that Bose is the ultimate profiteer behind it. If only Bose would apply the same level of engineering to their home audio products we wouldn't all have such a big beef with them.
I also don't think Pat would say they're the best speakers he's ever heard, he's certainly saying the sound the best for the application. The size and setup may also affect his opinion, even of the sound.