Good points. I don't cover that at all on the landing page.
It is 100% API driven using a a JSON REST api. As part of the open-sourcing process I'll be documenting that, but it isn't currently documented at all.
The pricing engine is lacking compared to other ERP implementations. Right now it does per-customer pricing with quantity breaks, but it doesn't have the concept of pricing libraries like others do. I do have experience implementing those but just haven't gotten it done yet. I agree that'll be really important for larger enterprises.
It is US only at the moment, mainly because I have no experience with VAT and European accounting. If someone was willing to work with me on it to discuss how it all works that'd be awesome...