I like how it's easy for clients to find me through their website, which is very useful when they need help with scheduling or finding an appointment time that works best for them! It would be nice if there was more variety in terms of pricing (e.g., some packages are cheaper than others).
Also, sometimes you have to wait longer then expected before your client gets back to you via email about whether he/she wants to book something - this can take anywhere from 1-2 days depending upon what package the user signed up for. This tool allows my business to see who needs appointments most often so we're able to schedule accordingly.