Actually, that's a slightly misleading title. You should trust
List<T>, but you should also know its limitations. Here is one of the dangers of launching into using new functionality without reading all of the documentation. I've been having trouble because a client application produces thousands of reports. These reports are supposed to be sorted in a particular manner. I've been sorting and sorting in SQL, and going not paying enough attention to test well. Results in production? Not sorted.
So naturally I started properly stepping through the application, inspecting results from SQL and in code. What do I find? That SQL is returning the proper sort order, but then the ordering is getting lost. Why is that?