It's easy to use, it has many features that are customizable depending upon your needs as well with multiple payment options available you can get what fits best in terms of pricing model! I have used so far only one feature which was invoicing but there were no issues at all when using this tool from start till now (2 years).
The UI could be improved by adding more colors or fonts other than black font/white background color scheme would do good too!! Invoice management system-easy way invoice creation & tracking processEasy billing methodologies -Multiple methods like credit card processing through Paypal etc.