Do not remove VS 2005 from your computer and install VS 2008 if:
1. You want to develop Business Intelligence solutions with SQL Server 2005, because VS 2008 does not support those projects (Report Designer, Report Model ...). Or to say, Microsoft does not want you to work on SQL Server 2005 with their own latest IDE!
2. You want to build Workflow (WF) solution for SharePoint. You will realize the old way in VS 2005 to install Features.xml is easier to use.