I use eclipse for other things and I really like it. Unfortunately I couldn't get the eclipse plugin working, and didn't feel like following that long list of instructions to do it manually. If you can get it to work, I highly recommend geting used to that environment, as eclipse is used in LOTS of different places (arduino, c, c++, java, processing, android...).
Well, I use Visual C++ Express 2010 since it's free, fast & and has all of Microsoft's Intellisense/Code-completion features built-in
I use it for writing code while doing compilation/uploading with Arduino IDE using the use external editor option. It takes a bit tweaking to make it work - but i found this simpler than Eclipse
I have just recently posted a HOW TO here on the Arduino Playground.
If you have the full paid version of Visual Studio, you should consider Visual Micro as posted by Wazzled.
I assume you've already been through Development Tools playground page.