I'm mostly grateful for it, to tell the truth.
For one thing, when I transferred to public school in 8th grade, I was far ahead academically compared to my peers - much as I rejoiced in no longer having to wear a uniform to school, I felt like I was surrounded by uneducated dolts, which was frustrating. I had been a straight-A student for my whole school career, and it took actual work to maintain that. Once in public school, I continued getting straight 'A's, but I could do it with my eyes closed and one hand tied behind my back, metaphorically speaking.
The other thing I've always loved about my Catholic education was growing up steeped in Latin. I sang in choir all through grade school and by the time I was in 4th grade I knew 4 complete Latin masses by heart. We weren't taught Latin formally, but I soaked it up like a sponge and it formed the basis of my lifelong love of etymology.
For that, and for many other reasons, I have long considered my Catholic school experience to be a net positive in my life - for all that I'm an atheistic animist/Buddhist these days.