I've actually done a few years of Northern Praying Mantis and it is a great style. I have studied other styles but I have a soft spot for mantis. It has a lot of quick parry/counter moves which usually result in the breaking of limbs. It is fast, lethal and unpredictable.
The only deficiency I can see is that it is complex and not as efficient as something like Jeet Kune Do. However its wide variety of high/low combinations make it more flexible. I highly recommend it.