Good service and support, but has some incompatibility

It’s a useful plugin and service. The support is excellent.

The service sometimes has problems (e.g. not applying the right VAT for a few days ending up dozens of invoicing mistakes exported to Xero – a lot of manual work to fix).

There’s a severe incompatibility with WooCommerce’s Subscription module: when you use your WooCommerce with VAT inclusive prices, the VAT calculation is wrong as soon as a subscriber manually renews his/her subscription (e.g. after a failed automatic charge). The Quaderno support is constructive with it, and the WooCommerce Subscription plugin developers are said to work on it, but this has been reported for months now without a result).