I am an unabashed fan of Brooklyn Ice Cream Factory. I feel like I have been going there since before they became a tourist bus stop, and it doesn't seem as though the quality has suffered, but there are a few things to know...
(a) Re: Hype - the problem with hype is that sometimes your reality don't live up to whatever mental expectations you have built up.
(b) Price - it is not cheap. These are NY prices - $5.50 for a double scoop, and the more exotic things like sundaes, splits and shakes only go up from there.
(c) Service - There is a line - expect to wait - any time of day/night.
(d) Location - There is very limited street parking nearby, especially at peak times.
These are the ways to combat these things...
(a) This is probably not going to be the best ice cream you've ever had. It is good...it is really good. They make small batch, simple flavors, and use high quality ingredients. Still, you may think you've had better elsewhere. Part of going there is the whole experience. Walk out on the dock behind the store. My first visit there was at night in the spring of 2002. My buddy took me out to the dock and told me to look up. It was the first time that I had seen the lower Manhattan skyline without the Twin Towers. It was striking...and a moment that I will never forget.
(b) The price is not cheap, but I don't know many who walk away feeling like they didn't get their money's worth. I am spoiled because my friend's wife used to work there and about half the time I go, it is with them, so we end up not paying for the stuff. The last time we were there, we discussed the rise in prices...and their conclusion was that BICF has become so popular, it is almost becoming a game with the owners to see how much they can raise their price before people flinch. As long as they have a continual line out the door, it is tough to criticize their pricing.
(c) When you get to the front of the line, you should have had plenty of time to decide what you want. Don't gum up the line...or you will be ridiculed - not by the staff, but rather by the real New Yorkers in the line who think you are a moron!
(d) I recommend taking public transportation, or as billyboy suggested, walking across the Bridge. Their is a subway stop about two blocks away, too. The nearest parking garage is nearly as far, and will cost you a pretty penny. Street parking is almost non-existent.
I do think that it is a worthwhile stop, and I tend to make it there at least once whenever I am anywhere near the area.