It’s decent.
I tried ChiTuBox recently and didn’t like it as much. It installed a lot of dependencies I wasn’t thrilled with, and I can only hope I disabled all the telemetry and such (others have had spyware concerns). Certainly there are lots of others out there who use it regularly and like it.
Manual supports in Preform is super simple - you just click where you want it to touch your model, and the software generates the lattice. You can control the overall touchpoint size (for automatically generated supports) as well as the size for each individual support that you add. If you have more complex needs, I recommend Formware which I recently used over in this thread.
Preform does a great job at letting you step through the layers to preview how each layer of your model will print and distinguishes support areas (orange) from your model (blue). The auto-orient isn’t particularly special and you can often find better orientations on your own. It identifies unsupported minima and cupping, and highlights areas it thinks needs more support in red (well, most of the time - occasionally there have been slightly buggy releases that make that functionality a bit wonky but it worked fine last I tried). It’s highly tailored to Formlabs printers and takes into account which material you’re using.
Other slicers can be used, as long as they export an STL (or similar). Just import the STL into Preform and print directly on the base. It prints just like any other model (dashboard still works) and you can still take advantage of Preform’s red shading to identify if the model is sufficiently supported.