I've used Wave. Has the most functionality of any free version. Customer service is also good. While its pretty seamless, there's also some quirks I don't like about it (mainly with receipt uploading and manually reconciling invoices to bank transactions). If looking for a paid service though, I've also heard Xero is good.

I used Wave when part of a startup, we did it to save money, but we eventually had to move to QBO due its functionality and integrations with other services. The move was good for us to help us deal with our growth and the growing complexity of our books. Made life a lot better when we moved off of it. This was 7 years ago so please take with a grain of salt, it may have improved dramatically but all the accountants I deal with only recommend xero and qbo.