Note: this post is obsolete. Please use newer version: http://blogs.msdn.com/webdevtools/archive/2008/11/29/spell-checker-update-2-2-full-support-for-vs-2008-sp1-simpler-setup-and-a-few-bug-fixes.aspx 

Bug fixes:

1. <param>Text</param> was not handled correctly.
2. Comments in <% %> blocks were not included in spell checking.
3. Spell checking terminated prematurely under certain conditions after encountering <% %> block.
4. REM VB comments were not always handled correctly.
5. Vista setup issues fixed (hopefully)

New features:

1. It is now possible to add word to “ignore” list. The list is global and is stored as a text file.
2. You can also add words to the Office active custom dictionary.

More details here

Visual Studio 2005 Add-in download

Visual Studio 2008 Add-in download