I, too, was really intrigued by the "does renewing work" line in the email. ;) (Hoping there might be some additional information on the topic...)
Ever since the proposed change to move the searches to more "relevancy" rather than "recency", I'd been wondering if renewing was still going to help with sales. (I have always thought it helped tremendously to renew ... and especially my most "hearted" items to hopefully make it into more treasuries, or better yet, get a sale.) I had read that Mondays were the busiest viewing days on Etsy, so I focused on renewing earlier in the week. Although, I do renew at least a few things almost daily.