The title pretty much sums it up. Now that we have List<T>'s why would anyone want to use an ArrayList instead? The only reason I can think of is if you are forced to use an old version of .NET before List<T> was implemented?
5 Answers
ArrayList is mostly for backward compatibility. In a project when there is a deadline, you may have the time to convert everything from ArrayList to generic List.
Another reason is that you may be using a library that is written in .NET 1.1. So you may force to use ArrayList in your code, and most likely convert it to a generic List for easy coding.
However, there are some differences and you may want to read this: .NET: ArrayList vs List
List<object>for the sake of consistency.