We use it to super-charge our SharePoint sites and specifically the Lists and Document Libraries within them. It's a brilliant tool that works well and also empowers teams to have their own advanced SharePoint users (Site Owners) who can also use this tool.
Pros
SharePoint native feeling UI
It's expression builder function
Speedy performance. It's not laggy.
A really well thought through product that meets a really key need in the SharePoint information governance space.
Cons
Ability to change text and fonts. i.e. make them bigger, smaller, more colourful, etc.
Ability to embed a Power BI widget / webpart into the form. Much like the 'data lookup' data connector.
Ability to embed SharePoint calculated columns in the form
More example / tutorial videos on difficult use cases and situation, particularly in the use of the expression builder.
Owww a Gantt Chart product!
Likelihood to Recommend
We've used lightning forms on literally dozens of our SharePoint sites now and it's just excellent, especially because it doesn't interfere with our ability to governance and administer the sites.
When first starting to use Lightning Forms, we had fairly simple use cases including a light touch Contact Management tool to allow colleagues to request a callback on behalf of a customer, and a Repair Request & Track tool for people to request a repair to their property and track its progress. While simple, these two cases have been largely successful and popular internally.
We are now looking to more complex use cases, including revamping our void property reletting process. This will bring together a number of departments and allow them to work together on each void in a visual way, giving everyone access to real time information and updates. This is particularly vital considering our colleagues work more remotely. We feel this solution is very powerful and is helping us strive to be sector leaders in this area.
Pros
Simple user interface - users of the forms intuitively aware of how/where to input information. This is in part due to being able to show or hide different questions or areas of the form, and making them required or not, based on previous answers.
Low/simple code - building complex forms with automation and multiple dependencies or lookups is relatively easy once you get started. You have the power of JavaScript to use and do some quite clever things if you can get to grips with it - a lot of solutions are only a Google away.
As it is based on SharePoint, it integrates perfectly with the rest of the M365 suite. Things like PowerAutomate enhance its functionality even further.
Cons
The styling of the form can sometimes be slightly awkward to use depending on what you're looking to do. For instance, if I was looking to highlight fields that users have missed (left empty), I would need to set up a validation for that question and then set a style for that particular field for when it is invalid. When you have a large and complex form with lots of dependencies, this is awkward.
Support for complex and niche issues is slightly lacking in my experience. I submitted a helpdesk ticket for help with a strange issue I couldn't figure out, which took several weeks to get a response to. Because it is niche, it's more difficult to find an answer by searching the internet. Luckily, knowing there is likely to always be a fix if you find the right place/use the right formula, I manage to resolve the issue with some trial and error.
It is disappointing that Lightning Forms does not integrate with the MS Lists app. Having the ability to access the form through the list app would add in a lot of useful functionality, including a better experience for users when taking photos to add as attachments.
Likelihood to Recommend
Overall, there are many use cases for which Lightning Forms provides a slick, easy to develop and extremely useful solution. Request forms that need to be actioned and inspection forms are the scenarios that we have used them for so far, which have seen a lot of success. We have decided that other scenarios that are perhaps more sensitive, for instance forms that may contain special category data relating to our customers, are less appropriate given the permissions/licensing constraints of both SharePoint and Lightning Forms.
