I wouldn't say they are radically different from any other engine layout really tbh, as opposed to a rotary engine for example.
Yeah true. Rotary is the most unique shiz I've ever seen. I still don't understand how they work exactly. Research time for me!
However, the boxer doesn't just change the engine layout, it changes the whole chassis.
It allows the centre of gravity to be much lower, which is why Subaru have decided to increase the Outback's ground clearance.
Also, if it weren't for the boxer, then you need a completely different system if you want to get AWD.
Of course, AWD is not ideal in every situation (Harder to drift or burnout), but then again for everyday driving, I would much prefer AWD.
After comparing a brand new front wheel drive, two other FF's, the smoothest acceleration has still been in a 90's AWD.
You don't get that cradle rock up or down when accelerating.