Depends on your lifestyle but I cannot imagine getting by without one. It is not used every day but it is handy sometimes and necessary other times.
Especially if you plan to have more than one kid, register for a good stroller. This may not be possible at Babies R Us - not sure which brands they carry. I LOVE my Peg Perego stroller (higher end - not sure of the specific name) with double wheels both front and back - it is not hard to maneuver if you have the correct wheels locked in position.
Get a neutral fabric - something your dh wouldn't be embarrassed to use (ditto for Bjorn fabric!) Denim or navy is always good. Nice thing about the more expensive strollers too - you can choose from a variety of fabrics - pick one that is unusual and easy to find if you are at the zoo, fair, Disneyland, airport, whatever. I got one that the girl who helped us hated - called it "man tie fabric" - but I have loved it - never shows dirt (kind of a dark taupe color with navy trim).
I would never use one of the cheap umbrella strollers - I agree with others who say that it is just painful to see a little one so unsupported and hunched over. The better (more expensive usually) strollers are usually much lighter than cheaper ones of the same size.
Do make sure you can pick it up to load in and out of the car. We recently bought a double stroller used from a friend. I love it and it is very useful (dd2 was 2 when dd3 was born) but boy is it heavy to lug into the back of the SUV....
When baby is very little, I just use the front pack or put the whole car seat carrier in the grocery store or Target cart. When baby is big enough, you can use the kid seat part of the cart. I know that freaks out some people who are sensitive to germ issues but hey, I live in the real world and my kid sits in grocery store carts... But at places without carts (like the mall) it is nice to have a stroller. Kid gets to see stuff from a safe vantage point - you can always let them out if they want and it is ok. Nothing saying they have to stay in it for hours at a time.
My main use for it is to walk to town. We live a couple of blocks above downtown and love to walk downtown to the library, post office, grocery store, Mexican restaurant for dinner. If I put baby in the front pack then I would be carrying library books, a bag of groceries, the mail, and our doggie bag from the restaurant - along with my infant, her diaper/wipes/blanket/etc. and keep my 3 year old and 7 year old fairly near me on the right side of the road! Good luck with that!
Sure, walking is good for kids but how far do you think you can reasonably expect a 16 month old to walk? Throughout the entire zoo, fair, walk around the lake, etc.? If you have a stroller, child can ride some and walk some. Use the stroller to hold your diaper stuff, snacks, water bottle for mom, etc. You want a cup holder for you by the way. Gotta stay hydrated while nursing!
Yes, you could get by without one but it makes life easier. Why not? If you are a loving parent, putting your child in a stroller now and then will do no harm. And if someone buys you one then all the better. Dh's aunt asked what we still needed while I was pregnant with dd1. We said stroller. She asked which one we wanted. I had picked one that was high $300s. She gave us $200 to put towards it. We paid the other $200 (that pesky tax...) This was seven years ago. But we are now happily using it on our third daughter. You get what you pay for. Go for quality - especially if you plan to have more than one.