Yes i think it is a very good idea for taxis to deliver ice cream in 144 cities worldwide. There is a lot of people in the world that like ice cream, and I think that it is a good and efficient way for them to get it. As long as the ice cream stays cold, then it is all good.
It's difficult to see how anyone could think that being able to order ice cream wherever you are would be a bad thing. If people don't like the idea of the app, they don't need to use it. The only real bad thing about it is that it won't be available in even more cities!
As a parent I think it is a brilliant idea. There are many times when you realize you are out of something that the kids want, and do not feel like taking all the kids to the Store to get it. I think this idea could really take off and would leave the door open for many more products.
If Uber can use it's current service to branch out past just people transportation, they could be wildly successful if they jump into the right new endeavors. Ice cream is the first product in a line of many that they could have the drivers delivering. Uber's drivers are gaining a little more loot on the side and making life a little better for the rest of the world. Great plan!