My experience in Australia with Markbass has not been a thoroughly good one.
First off, may I say that they are excellent-sounding amps, and very light for the power. Their cabinets are equally portable.
However as Cherns has said, their distributor network is not very comprehensive, and existing distributors have mixed up orders very often. The amps are also not very reliable. There has been a 20 - 25% return rate, mostly due to power-related failure. My guess is the need for low weight has compromised somewhat on reliability.
Bear in mind though that most returns were touring bands. Definitely not as hardy as the Edens or Hartkes.
Tonewise, they are incredibly versatile and the filter systems in the pre-amp make quick changes from 'vintage' to 'modern' very easy. They are also incredibly high-powered for the size. A 500watter weighs as much as my laptop.