Curse has released a premium version of their add-on client. The service they are offering goes for $30 a year on their annual plan, or $5/month if you choose to pay like that. There are some features of the premium client worth looking at if you're interested in spending the money.
The premium client offers one-click updating of all your add-ons, which is a very nice feature for those of us that have a few hundred of them floating around. When I tried this earlier today the updating went smoothly and without any problems.
Another feature of the premium service is that you're not subjected to all the ads on the Curse website while you're logged into your account. This is good if you're still going to the site often, but I'm not sure how often you'll go to their site if you're using their add-on downloader client.