I dont use Buy It Now (or at least I didnt when I could just go to Maelstrom) as it tends to be folks who have bought stuff cheap from Maelstrom/Wayland/GW Trade Account and are just reselling it at a markup, though often cheaper than GW. I'd probably shy away from these people now as well, as ultimately the money you spend will go back to GW as they restock. Plus the second hand stuff is often cheaper.
Plus, I do like bidding for stuff, it's kind of fun.