If you are big I think it makes sense to control every part of your business but otherwise it's massive headache because of security and taxes, especially now that the EU wants to collect VAT for european customers even from companies that are outside EU, there are payment services that do all the tax things and even if the fees are higher if you are small it will cost you less and keep you focused on growing.
There are third-party solutions which can take care of tax calculations for you - these can be plugged into Kill Bill.
One of the main core values of Kill Bill is that you own your data: this is especially important if you focus on growth, so you can run real-time reports on MRR, churn rates, upsells, etc.
