Though it's not bad as a starting point, but the fact they have not improved anything and that it's very slow means you shouldn't consider it if you have more than say a few dozen invoices a year.
It's very very simple to use and to setup.
Nothing is ever improved. I've used it for a few years and will be moving. Speed is slow. Templates are a bit messy. Sending reminders manually is complicated.
Likelihood to recommend: 0/10
A free version is available for up to five contacts per month.
Professional: $5 per month for up to 100 contacts per month.
Enterprise: $8 per month for up to 500 contacts per month.
Ultimate: $10 per month for unlimited contacts.