Bought a sop 18 months ago - curly Elkhart, and very pretty. But, really hard to play compared with the tenor as there seem to be no margins of error. I have found that the mouthpiece seems to make a big difference. Just got a Link 7* which has been a big improvement - much easier blowing and a thicker, fuller tone. I still find that one or other register is in tune - if I tune to lower A, then upper A is sharp, and haven't cracked that. I also find that my lip gets sore very quickly compared to the tenor, which may be that I'm just trying too hard. That does seem better with the Link.
With all of that, really enjoying it - just being playing along with Gato Barbieri's duet with Carlos Santana on Europa - great fun!