Looking at one of these myself, maybe the medium/large how does it perform?
Very, Very well. I have had a Grand Turbo built in at my last home, that my step son owns now, a Weber Genesis SE at my new home and now the XLBGE and IMHO, the Egg cooks much better.
but.
It does have a learning curve.
Once you master how to control the temperatures my using the flue then that is the hardest part. It takes very very little airflow to change and maintain a constant temp.
So far I've cooked an 8lb pork butt, 2 - 14lb brisket and 8 Rib Eyes.
I do have an iGrill dual probe thermostat and I would recommend something similar, just because I like knowing numbers. This allows me to monitor internal dome temps and internal meat temps from my phone and to set warnings if a specific temp goes too high.
I'd also recommend reading the BGE website inside out, it is very helpful for 1st time egg owners even if you've been grilling for years.