I walked a bit in my first (4:31), but I really mean a bit (in the tunnel so no one could see me)...
However, I agree about rushing into marathons. I did and havent been back to the big one since - I've tried, but I just cant get over the trauma of the whole thing. The run and the recovery.
So I've stuck to shorter distances.
Would I be a better runner if I hadnt done the marathon (which seems to be your implication)? No.
I learnt a lot about myself, I learnt a mental toughness I didnt know I had. Most importantly, it gave me the desire to be better. I've never failed at something in such a spectacular manner before.
Do I advise people not to do a marathon first? No. I think if they are itching then they should do it. If only to learn the lessons I did.
My best adivce to newbie marathon runners is - you will more than likely suck, you will hurt, but like hangovers you will forget and you will be back (someday).