Multiple problems for me. I do not think this was ready to release.
1) When I search by manufacturer, I get a whole lot of non-related items by other manufacturers at the end of the list.
2) When I try to refine the manufacturer search using the left side options, all the extra items from the end of the list in 1) come into the list, making the left side options useless.
3) When I do a search on manufacturer, the resulting list is in some random order. It used to be sorted by category (amp-Multi, amp-ss, amp-tube, etc.), then by date of the posting, newest first. Also the new list does not say what the category is. For cables, for example, it is common to have the same name for interconnects and speaker cables. All of this makes getting a quick look at what is available for a specific manufacturer very difficult. Because of 1) and 2) you cannot reliably refine the search. Even if you can, it is a pain to have to refine, expand, refine, expand, etc. just to see all the products that are available from a given manufacturer sorted into categories. I would remove the classified/auction field or make it into a column with a C or an A and add the category back in, with the list sorted like it used to be. Better yet, let the user configure the sort order.
4) You used to be able to click on a seller's zip code and it would tell you where is was. This was handy especially for heavy items.
5) You used to be able to get estimated shipping costs. They were definitely an estimate, but still quick useful.
6) You cannot get feedback on a seller.
7) If you use the left side to refine the data, the screen keeps refreshing. If you select PreAmp, it refreshes the screen and you have to scroll down again to select the sub categories (e.g. Tube). Bad design. I would also have the left hand side list in a logical order (e.g. Amps and Preamps in the same section) rather than in alphabetic order. Instead now, it starts with Accessories, with PreAmps and Speakers at the bottom
8) Advanced search used to be very flexible. Instead of the new fixed price ranges, you could search on the range you want. $1000-$2500 is too wide in many cases.
9) I used to search by partially zip code (e.g. 01 or 018) to see what was available in my area. No longer available.
10) I used to search by country (e.g. Swilzerland) but cannot do that anymore.
Overall I think the navigation is not very user friendly, is pretty clumsy and that too much functionally has been removed. I understand some of what they are tyring to do, I just don't think this interface is ready for prime time, especially given how user friendly the old one was.