I mainly use the marketplace as a starting point when I'm looking for things. I've managed to find a few great designers that I liked from browsing the marketplace, and then if I really liked that designer I would visit their store in world if they had one.
I also like to sort the marketplace by newer items so that I'm able to see what is fresh and new.
I only read certain group notices, if I start getting spammed every 5 minutes with a group notice I'm not going to really pay attention to them anymore or I'll just quit the group.
The one thing I don't like is when the item does not match the picture in the store and looks completely different in game because it's been photoshopped a lot. I will not purchase again if that happens.