In the interim we are using our legacy system. I wrote a connector that uses the Shopify admin api to fetch unfullfilled orders and fulfill them.

Long term we are thinking Ship Station or maybe ZenDesks ecommerce offering.

O nice. If you're doing a lot of volume (1k+ orders/month) you might want to take a look at ShipHero. You'll begin running into inventory issues with ShipStation at that volume.

Disclaimer: I work for ShipHero.