The Swift was nice, felt fine straight out of the box, the B17 I had for a while, seemed harsher and harder to break in, that might have been down to the flex you get with ti rails on the Swift though.
Both are quite slippery when new, you seem to move about a bit on them at first.
Also, they used to streach when they got wet( or should I say soaked) too, even though I used loads of the prohide stuff, which is the reason I moved on in the end, got fed up slackening off the tension* and waiting for them to dry out then re-tensioning them again.
*not sure if this is what Brooks recomend when they goet soaked, but its what I used to do anyway.
Last off, my old man used to work for Brooks years back, he still has his 1st saddle, which must be 40-50 years old now!