After 6.25 months of running, I ran my first half in October. I'm 31 and lost 30 pounds over the same period of time. I was running about 30mpw on average for the final 2 months leading up to the race (yes, that means some 20 mile weeks as well, and only one 40+ mile week).
I ran a 1:38 and came in 90th out of 2,250 runners or so and was 5th in my age group.
Judging by the responses of my coworkers, it's an impressive time for the average person. For the serious but non-elite runner? Well, clearly not, though 'serious' is a very subjective term. I do take running seriously, but onlyvwithin the constraints of my lifestyle. I work a full time corporate job and am about to have my 3rd child - all of whom will be 4 and under.
I'm hoping to break 1:30 one day, though 50mpw is about all I can squeeze out in any given week currently.
1:15 is a dream, and I take running more seriously than most people that I come in contact with.