Zoho Bookings from my personal experience is best when you have a growing list of customers and need to get free of the hassle of taking written notes in your Rolodex. It's like a CRM but optimized for booking tasks. I believe it would be less suited, if you are a new business starting from scratch
It still needs more robust features and customization, like workflows and such. I'm confident they'll continue improving it, but some particular customization settings aren't available, in terms of triggers, content, look and feel, but it is mostly very detailed and particular. If you're ok with adapting to it, it is an excellent tool.
Some of the integrations and features are harder to set up. Once everything is set up its fairly straightforward, but if like ATI you have multiple branches or departments utilizing Bookings, you would need to set up separate booking sites for each office/salesperson
A lot of things are not great as this is a new tool, but they fix it relatively quickly. They don't have a direct phone number, but Zoho support has good service overall
I found the integration with the two above is great if you're a Google Calendar user which we are not. While with Zoho Calendar we can have two way integration with Google Calendar there wasn't a need to do so. With Zoho Bookings which also integrates with Google Calendar we didn't have to worry about that as the integration with our Zoho Calendar was virtually automatic. There was also the cost consideration as the two above have a free version it was limited and didn't have all the bells and whistles we needed. Zoho Bookings provide us with everything from a single sign-on web browser and mobile app
Zoho Bookings does not have either a positive or negative ROI as this is included with our Zoho Suite of features and we have enough licenses currently for anyone who would need access.
It would be a negative ROI if we needed to purchase additional licenses solely for our engineers or the entire organization, most of who do not need access to any of the other Zoho Suite of features.