A.R.
I had a tandem double stroller (it was a Jeep Grand Cherokee, which I don't know if they even make any more). Our nickname for it was "the beast". It was so difficult to steer, yet it had good reviews compared with others online with regard to maneuverability. One of the positives is that it fit most infant seats. But, I hated it.
Last November, I bought the Joovy sit and stand tandem stroller from strollers.com. It's much shorter, lighter, and one child has the option of standing or sitting while facing the parent, in the "back seat". The only issue we've had is that when the kids sit back to back, they bonk heads occasionally. But, we took it on vacation and the kids both wanted to ride in/on it and they loved it. I was happy with the price (same as Babies R Us) with free shipping and a discount for opening a Google account. It arrived within a week. And, they had some pretty cool colors. It was much better than trekking 30+ minutes each way to the nearest Babies R Us.
I highly recommend it, but might not be appropriate depending upon the age of your kids (e.g. if you're having twins or two very close in age). I bought mine when my children were 3.5 and almost 2. You'd have to check on what infant seats work with it (you can find out on the website).
Never had a side-by-side, but those always seem impossible to maneuver through aisles.
Good luck!
A.