Usually we plan our trips a little more in advance, but scheduling a custom tour with Andrew about a week out wasn't a problem at all (at least in December).
We like graffiti, good food, and learning about local history and culture - Andrew was able to accommodate all of this for us in a 4.5 hour custom tour of the Lower Eastside and Williamsburg.
In contrast we also did a highly rated food tour with another tour agency, and although the food was good, the area we saw was rather small, there wasn't much in the way of interesting local history, and we were in a large group of other people - so it wasn't customized to our preferences. I'd skip that and just see if your guide has some recommendations - Andrew brought us to this pretty awesome tiny jerky shop, and then we stopped for a wonderful orange drink in Brooklyn.
When we come back to New York, Streetwise will be at the top of my list of things to do. It's like walking around town with a friend who knows all the good spots to stop. The next day we even received an email with a couple bonus recommendations to check out if we made it back over to Brooklyn.
Overall, it was informative, tasty, and fun!