We moved the project over to VS2008 to stay as current as possible. WIth VS2008, we can develop both .NET 2.0, 3.0 and 3.5. The version for Events is specified as .NET 2.0. VS2008 sources files differ from VS2005 sources files (e.g. partial classes for the .vb design files in VS2008), it's a one way upgrade.
Practical (excuse?): I use my professional environment for DNN (my hobby/free time -if any-) development. My professional organisation (www.xcess.nl) is Microsoft Gold Cerified partner, we have standardised on VS2008 since the day it became available. I do not use VS2005 anymore (not on my PC). Sorry.
Suggestion (apart from upgrading your VS2005 to VS2008, which I can recommend): The Express versions of VS2008 are freely available from Microsoft and I think these can be used for development on Events as well.
Curious: what would you like to change with Events 04.00.00? Are these general ideas/suggestions/enhancements that we can review for 04.01.00?