For me, the tricky part were some of the options in the BOM. When to use a jumper, when to use a component, when to keep it open, etc. .
C15 - Leave out ( I put a jumper in by mistake)
R15 - Jumper
C22 - Leave Out, no jumper
R20 - Leave out, no jumper
C7 - Can cause issues. Wayne after the Pearl 2 article was published recommends leaving out.
Of course, double checking your component values before soldering - using the correct part. I got on a roll with all those 10R resistors and used them at R8 and R10 by mistake - they should be 10k! Also, good soldering, especially on the ground plane side of the caps, takes a little more to flow the solder well.
I learned a lot doing the Pearl 2.It took a lot longer than I planned - a couple months. Patience - number 1 skill.