Today I was reading Scott Guthrie's blog post about the LINQ to SQL. IMHO LINQ looks like the best tool for .NET since C# Attributes! Since the .NET LINQ to SQL Designer will compile a database context for you we'll never have to write stupid unit tests just to check if a query works (note: I said stupid unit tests). You'll know the query works by the old programming myth "Well it must work, it compiled!". Obviously we'll still have to test some queries, but you know what I mean. You change a column name or drop a column from a table and sometimes you don't know what parts of the application you broke until either your unit test fails, or if your unit test wasn't explicit and specific enough, when your customer complains that the report isn't working anymore.
Ever since Ruby on Rails came out and I actually learned it I lost my enchantment with ASP.NET - until now. Ruby on Rails still blows my mind with how easy it is to use, but I'm really happy that .NET now includes the AJAX framework and this excellent query tool.
The only thing I want from .NET now is Database Migrations in C# a la Ruby on Rails.