with in excess of 3000km on other recumbents (ICE B2 and M5 M-Racer), i'm finding the transition easier than i expected.
In terms of my progression, the B2 was the perfect starter 2-wheel recumbent, nice and stable, upright enough to balance easily. The M5 took a lot of getting used to, absolutely solid as a rock at high speed, downhill it's on rails, but a low speed nightmare. Very difficult to get used to, I think I had my a-ha moment about a year in when I realised I could ride it in slow traffic.
The CB by contrast, has been a lot easier to get used to. The pedal steer is far more noticable at start up where you need to use handlebar pressure to counter it, but like most other recumbents, pick a point on the horizon and lift your vision and it's much steadier.
The more upright position on the S40 gives a good view of the road, and it absorbs bumps better than the M5. I don't think I'd recommend the S40 as a first recumbent, if any CB, probably the T50 or Q45.
More thoughts and the build diary are here
https://adventuresofanathleticdiabetic.blogspot.co.uk/