Shaun - I use it on domestic and commercial alike. It's not cumbersome in the slightest, it's very nifty! It's actually a shade lighter than a Dyson, believe it or not.
I totally agree about the nozzle thing. Your only option with this machine is ridiculous if you want it to do upholstery and stairs too. You have to order a separate nozzle kit and when you want to use it you must:
> unscrew the little grub screw in that round black plastic thing on the front
> Remove the plastic thing
> use a special tool to unhook the drive belt from the brush strip
> insert the nozzle tool
> do what you need to do with it
> repeat the whole process in reverse to turn it back into an upright again
Absolutely silly!
I carry a small but very powerful Electrolux UZ cylinder vacuum with me too, I use it for going round the edges of rooms, stairs and upholstery. Far quicker than dismantling the Royal and putting it back together again :

But don't get me wrong, I wouldn't swap the Royal for anything right now, I'm smitten by it

Robert - It's not a clone, Royal have been going since 1904 or something like that, and probably haven't updated the design much in that time either! Maybe Kirby copied them, I don't know!