I love BETSI and tell people that whenever I get the chance. It's already a great tool at a great price but Graeme (the developer) is wonderful to deal with. He really listens to Etsy sellers and implements new things all the time. He stays on top of the frequent changes that Etsy makes and makes sure that the software always works like it's supposed to.
BETSI is basically a one stop shop for all of your Etsy changes. You can change titles, descriptions, categories, pricing, tags - basically anything that you could change if you were in the listing itself. But BETSI does it for any or all of your listings including those that are active, inactive, expired or sold out. You can also change your categories, shop announcements etc on there. Changes that would have taken me days to do now take a few minutes. There is a BETSI free version but there are some limitations to that. It is well worth the price to pay for the full version. I get the yearly subscription. It's a bit cheaper. There is a free trial which is pretty smart on Blugrin's part. I tried it and was hooked forever! I don't believe that I could run my etsy shops (I have it for 2 shops) effectively without it now.