Kew, I love hearing positive stories like yours. You and your boy are obviously very special people 
DD was born at 35 weeks, so not very prem, but had stopped growing in the womb at around 30 weeks. She was 3lb 3oz.
She was very hard to feed, little and often was our mantra. I spent the first 6 months of her life in a daze I think - she fed every 90 minutes. She spent a month in Kindertensive and was just under 5lb when they let her go home. She was only 23 cm from head to toe!
She was an early talker, but late crawler and walker. She was tiny until she was about 3/4, (wearing prem clothes until she was 1, then 18mths to 2 years clothes until she started school), then suddenly shot up and is now (at 8) one of the tallest in her class.
She has no developmental issues, is very fit and generally healthy and (I think) quite clever - she seems 'old for her years' if you know what I mean. Her eyesight was a worry in the early years, but got stronger and is now quite normal.
I often think the only 'hangover' that she has is that her chest seems 'weak'. Every cold she has tends to go straight to her chest and wipes her out. Although she copes with them very well and rarely needs time off school. That's only my opinion though, and my mum always says that I had a 'weak' chest too.
Emotionally she seems fine, we didn't suffer too much with the terrible twos/threes, but we have always kept her very busy which helps I think. She is very much 8 going on 18 so maybe she is saving the worst till her teen years!