We have found the Steven’s financial aid office very straightforward and helpful, and have had no surprises with our tuition bills, etc. What they said on the phone matched what we were charged. Not sure about CSS affecting financial aid - we received +10K more in financial aid than our expected family contribution said we would. DD is a Stevens Pinnacle Scholar which means she was in top 10% of admitted students.
CSS is not required for Stevens. They do factor family income into their Merit Scholarship offers. This is why you will hear about students with lower grades getting more in Merit $.