I have a Kelly Kettle with nearly all the extras. (The ones it came with about 5 years ago)
Good points.
All in kit and you can cook just about anything (using the extras like the hobo stove etc.)
Main Kettles are one of the best and quickest ways of boiling water, barring a JetBoil or similar, and certainly the best using fire.
Great if you are carrying in your car, mainly for hot drinks.
Bad Points
Bulky, takes up too much space for what it does.
Messy once used. Fire always is sooty, but at least it's mainly contained to the fire base and the internal tube of the kettle.
If you are not using the Kettle and you're cooking on the Hobo stove (or Ghillie kettle equivalent) then it's a real pain trying to maintain heat. You're forever feeding little sticks and twigs onto it to keep it going, which keeps cooling the fire, then burning out, then cooling etc. Really fiddly.
Fire base is small (middle sized stove) so pan size is limited.
If you like the idea of cooking with fire, I would suggest the Firebox Stove range of fire boxes, which are far more versatile. They also have a sale on at the moment.
www.fireboxstove.com
I have 3 of their stoves (different sizes) and I love using them. You can use them with twigs and larger wood, charcoal, wood pellets and they're even designed to be used with both meths and gas Trangia burners. Maybe worth a look and far better, in my opinion than the limits of the Kelly Kettle set up.
The chap who invented them has a channel on YouTube which is great viewing, especially the earlier ones on how to use the stoves.
Hope this helps.