The new bike is set up with contact points that are identical to the TTX, so she does feel much difference at all when riding the two bikes. However, the new bike does seem faster for her given the very limited data available. Her two fastest TT efforts ever were the first two races (Putah Creek and Master's Worlds) on the new bike. Equipment wise the only difference between those TTs and the ones she has done for the last couple of years (many Putah Creeks included) was the bike frame. Conditions were good both days, but neither ride was partiularly close to her season best power output for efforts of a similar length. So she is pretty happy about how the bike has raced, even without the integrated bars.
Outside of the soon to be resolved UCI issues (which proved to be irrelevant this year because of lax enforcement) a small downside SC relative to the TTX is that it is hard to adjust the front brake width quickly. This prevents her from choosing her front wheel (H3 or 1080) just a few minutes before the race to match the wind conditions. This probably cost a couple of seconds on both of the TTs mentioned above, because of my bad pre-race guess about the conditions. I think there might be a way to solve this when using the steerer-stub by placing a cable adjuster in-line. However, I am not sure that would actually work given how the brake operates, and don't think a similar solution would work with the integrated set-up.
All in all, she really likes the TTX , but likes the SC even better.