I had the 1250S - the half-faired version, but with exactly the same seat/footrests/chassis etc. The engine is lovely; smooth, quiet, fuel efficient, lots of torque. Bear in mind that fuelled up the 1250s are over 270kg, so it is somewhat cumbersome at low speed with a pillion. My 20 year old daughter (and frequent pillion) is 5'3" and slim and she hated it - no legroom and the sloping seat meant she was sliding forward during braking and cornering. Another frequent pillion of mine did one 150km run on it. He is 6' tall and lightweight, and when we got home his legs had cramped from the position and I had to help him off the bike. He would not get on it again and my daughter also stopped riding it after a few 100km runs as it was too uncomfortable for her.
Both of them are fine with my other bikes and I've been carrying pillions regularly for years and can ride very smoothly with a passenger, but the complaints have been the same from everyone who rode on it - no legroom and a slippery, sloping seat. (If your pillion is used to riding on sports bikes with their knee-high pegs that may not be an issue, of course.) The pillion rests can be lowered - but not easily if you have pannier racks as they use the peg mounts. I put one of those anti-slip covers on the pillion seat which helped to some extent.
Check one out with a passenger first.