How fit does cycling make you?

I cycle to work (25 minutes each way) about 3-4 times a week. That's 150-200 minutes or 2-3 hours of cycling per week. It's not massive strenuous. There are two hills each way, i.e. 4 hills per day i.e. 12-16 hills per week.

If I stopped doing this cycling, would I feel the difference do you think? In other words, is this cycling making a significant contribution to my fitness?