excel interop alternative

Take a look at the EPPlus project over at Codeplex:

http://epplus.codeplex.com/

I recently used this and it worked very well. (VS2010 and .Net4)

EPPlus is a .net library that reads and writes Excel 2007/2010 files using the Open Office Xml format (xlsx).

Nice example page: http://epplus.codeplex.com/wikipage?title=ContentSheetExample