I think you need to be more specific and give constructive criticism.
I have to say the old layout was much easier to navigate. With the new one, lets say I want to look at skimmers. I now have click 4 links and visit a total of 5 pages to get there which is incredibly annoying.
[Home Page] Shop Now>Dry Goods>Aquarium Equipment>Protein Skimmers
I
can "hover" over it with my mouse, but if I move too fast or slightly on an angle, the menu disappears and I have to start from the beginning (I'm sure we have done this on other sites, and how annoying it can be)
I think a vertical side menu w/ filters is a smart idea [when implemented correctly] but should be in its own 'frame' and not load an entire new page just to get there. Keep what is on the screen to the right, where you can navigate through the menu, and the right side of the page changes when clicking on a link.
Here is an example. Click Shop Now, and then when you hit the links with the + beside them, a sub menu pops up below it, and you can navigate much easier. A click would be required and no more hovering.
[Home Page]
*click*
Shop Now
[New menu opens on left side page]
Dry Goods
+Aquarium Equipment
++Protein Skimmers [Right side of page opens showing Skimmers when clicked]
I hope that make sense...