I've decided to use the latest technology (that has a final release).
I have tried to compile Pcap.Net with Visual Studio 2010 and Target Framework 3.5 but I compilation error that I've reported to Microsoft: https://connect.microsoft.com/VisualStudio/feedback/details/560606/c1001-compiler-crash-on-c-cli-project-in-vs2010-when-target-framework-is-3-5
If you want to have future version of Pcap.Net then my only solution to you for now is to upgrade to Visual Studio 2010 and use .NET Framework 4.0. If there is a high demand for Visual Studio 2008 (you can open an issue and then people can vote for it) I'll
try and see what I can do.