I remember being in floods at 4 because my brother (1y older) was going to school and I so wanted to go too... twas crap when I finally got there but I loved the idea.
dh is German, summer bday and didn't start until 7, which meant not finishing until 20, then, due to national service and the way the HE system works in Germany, not graduating until 28. It hasn't held him back as such, but it has made our lives a little more difficult.
General starting age is currently 6 in Germany, with the option to hold your child back a year or (recently) put him/her in 6 months earlier. Paediatricians do a school readiness examination thing at age 5. I don't have an issue with the starting age per se, but more with the attitudes around it - learning is (at least was until very recently) demonised before the start of school, as stealing children's 'childhood', and then, after the start of school, the pressure piled on (IMO) very fast - most federal states split up children to three ability-based school types at age 10, and going to the least academic of these types is widely considered to be an utter catastrophe. I would much rather have an earlier but more gradual, or at least less 'loaded', start to formal 'learning' (oh, and a proper comprehensive system and the option to HE, but my dses will probably be parents themselves before Germany introduces those).