Subscribing on Bandcamp gets you a multitude of things. First off, you get the entire Lowercase Noises discography instantly. Second, you get a collection of songs that are exclusively available to subscribers, which will be added to periodically. You're the only one who will be able to download those songs! And third, you get an automatic 15% discount on all merch.
There's more to it, so if you want to see what it's all about come check out the page on Bandcamp.