This time around, I tried a different blouse pattern — this one has fewer separate pieces and more darts. I find darts pretty easy, whereas lots of separate pieces sometimes leads to great geometric confusion on my part. I sort of wished I’d done one of the other patterns in the set (it came with 9 different patterns, I think), which had even fewer pieces!
I’m not sure why one would want a separate midriff piece — I guess it makes it easier to get it close-fitting there? And it does let you do it in a contrasting fabric, which can be particularly helpful if you’re short of your main fabric, or just want to do it for design reasons. Maybe I’ll try that sometime.