Green & all,
I had a whole long reply typed up and lost my network connection and 30 minutes of typing.  Here’s the short version.
I work at a running/tri shop in a very family-oriented neighborhood in Brooklyn.  We sell a LOT of jogging strollers, so we looked very carefully at the market to choose the best.  The answer: the BOB SUV stroller.  I have used it myself for the past two years and LOVE it.  Our customers send their friends to buy one because they love it.
The basic model comes in 3 colors, of which black is by far the best looking.  There’s also an “Ironman” M-Dot branded version if you want your future star to help keep WTC in business. 
There’s a lot of things to like about the stroller: it’s light, it folds easily, it has a relatively short wheelbase so you can maneuver it, it’s narrow so you can get it through doors, it can carry up to 70 lbs of kid+gear.  It’s got reflective tape in a lot of places.  It has a handbrake with a lock.  All three wheels are quick release so you can store it and fit it in your trunk easily.
The best feature of the BOB isn’t in the stroller, it’s in the weather shield.  The weather protector for the BOB wraps completely around the cockpit and does such a good job keeping out wind and rain that they cover it with warnings reminding you to make sure the air flap is open in the back or you’ll suffocate your child!  It’s an obnoxious bright yellow that only a cyclist would appreciate, but in bad weather you will certainly be seen.  (Plus, it looks good on the black stroller.)
They also sell a “console” that attaches to the handlebar that holds two waterbottles and has a pocket for extra stuff, like money or kid snacks.  Didn’t know about it the first year, now I wouldn’t know what to do without it.  Very convenient.
In addition to the BOB, you’ll want a bag to put your kid(s) in to keep them warm.  I use and highly recommend the Nano bag, which has a wind resistant outer layer of nylon around a warm fuzzy layer.  It zips up to your child’s chin and keeps him warm & toasty.  I had my son out in January in 10 degree weather with the weather shield and the Gaga bag (Nano bag’s bigger cousin) and he was fine.
As to age: jogging strollers do nothing to support the kid’s head, so they need to be able to hold their head up.  I think 6 months is too conservative; if your child can sit in a bouncy seat (the kind with the spring that hangs in a doorway) or a saucer and support himself, he’ll be fine in a jogging stroller.  For my son, that was 4 months.  For my daughter, it’ll be 5 months, probably.
To answer your inevitable question about a seat for the back of your bike, wait until at least a year.  It’s one thing to hold your head up, it’s another to do it wearing a helmet.  Plus, baby’s skulls aren’t fully formed and a crash could be … very bad.  I do have my eye on a behind the bike trailer for both kids, so I can be the only person in Prospect Park in my aerobars hauling a trailer up the hill. 
PM me if you want prices or more info.
Lee Silverman
JackRabbit Sports
Park Slope, Brooklyn