I used to love .NET Reflector back in the day, but ever since Red Gate Software took over it has gone downhill dramatically. Now it forces me to update (which is absolutely ridiculous), half the time the update doesn't go smoothly, and it is increasingly hindering my productivity with each update. I am sick of it, and I am ready for something better. Is there a better disassembler?
Update:
List of various alternatives mentioned in answers -
Also take a look at ILSpy by SharpDevelop. It's in early stages of development and they just made a release on the 24th of February. That in itself works pretty good for me. From their website:
ILSpy is the open-source .NET assembly browser and decompiler.
Development started after Red Gate announced that the free version of .NET Reflector would cease to exist by end of February 2011.
Update: JetBrains has released dotPeek, its free .NET decompiler.
Update 2: Telerik also has a free decompiler: JustDecompile.