I picked up TidyCal when I got tired of paying monthly for what should be a solved problem: letting people book time with me without the back-and-forth email dance. If all you need is scheduling not invoicing, not payment collection this is one of the easiest lifetime deals to justify on AppSumo. I only say that because I only use it for scheduling so cannot comment on payment features.

Setup took maybe ten minutes. You connect your calendar, define your availability windows, create your booking types (30-min call, 60-min consultation, whatever you need), and you get a clean booking page link to share. That's it. The calendar sync works both ways, bookings show up on my calendar instantly, and busy blocks I've already got are respected so there's no double-booking. Buffer times between meetings, daily booking limits, and minimum notice periods are all configurable, which matters more than you'd think once people actually start booking.

What I appreciate most is the simplicity of the booking page itself. It loads fast, looks professional without any design work on my end, and visitors can pick a slot in two clicks. Custom intake questions let me collect context before a call so I'm not walking in blind. Automatic confirmation and reminder emails go out without me touching anything, and the timezone detection handles the conversion for the person booking a small thing that eliminates the single most common scheduling screwup.

A couple of honest notes: the interface is functional rather than flashy, so if you want heavy branding customization you'll hit limits. And group/team scheduling features are more basic than the big enterprise tools. But for a solo operator or small operation that just needs reliable, unlimited booking pages, none of that matters.
The real comparison is the math: Calendly's paid plan runs around $10-12/month forever. TidyCal is a one-time payment that paid for itself in the first few months, and I've had zero reliability issues since. Five tacos if you book calls, meetings, or appointments of any kind, just buy it.