I am still in the beginning stages of using Marketworks but I am very impressed with what they have to offer. It is true that their system is complex, but it is something that can be learned and will allow for more time in the future. I think that this auction solution is for the serious eBayer. If you want to grow your business or pull it all together into one solution this is it. They offer integration with many outside solution (excel, etc.) and they offer a store front with your own www.com(unlike some of the others). I think this solution will work for small time sellers that have the intention of growing and although you can use as many or as little features that you choose I don't know that this is for the PT seller (my opinion).
I gave it 4 stars because I think the navigation of the system and custom terms that they use can be confusing, but as I said earlier, it can be learned. They are currently tweaking their system so we shall see what changes that will bring.
UPDATE: I just wanted to say that I LOVE Marketworks 5 Stars. I think that they have it all and their new interface is much easier to navigate. It still takes time to set up your specifications, but it is worth it, because you can customize and streamline your business. They have also implemented many new help features for the new user. I would recommend them as an ecommerce and auction solution.