I love this store. I haven't done any price comparison shopping so I can't really comment on the other posters' experiences, but that's because what's great about Kol Kid is they have unique things I can't find anywhere else. If you need basics it's probably not the best place, but if you want to treat yourself or someone you love you can't go wrong. When my sister found out she was having twins that seemed like the perfect occasion to splurge on very adorable $20 onesies. Usually I'm all about the Carter's outlet $12 six pack of onesies (which you won't find at Kol Kid).
The staff is friendly, helpful and knowledgeable, and in spite of the high-end nature of their stuff they are incredibly mellow about strollers and toddlers running around. I also love that they always have new stuff coming in, so even though I browse every week or two (I live very close to the store) there's always something new to look at.
If you tend to be a frugal person or a bargain hunter, it's definitely not the place for you. If you want to splurge once in a while (or you're lucky enough to be rich!) it's a wonderful place.