The fact that it's easy to use, has a lot of features, and allows me to add my own data. I dislike how outdated the UI is - there are so many things that look old fashioned and just don't work well anymore. I would like to be able to see the entire invoice history for each customer in one place. Also, I wish you could add multiple customers at once (which you can with other services). I'm trying to find a way to keep track of invoices and payments without having to create new accounts for every