having our moss 2007 all our developments and customizations were based on smartparts
everything in our sharepoint are smartparts (some smartparts using jquery)
but i couldn't find the smart part plugin for moss 2010, is it possible to use our existing smart parts in moss 2007 in a new installation of moss 2010
The Visual Web Part in SharePoint 2010 is essentially Microsoft's implementation of Smartpart. If you have User Controls/ASCX files working for Smartpart, they should work fine with the Visual Web Part in 2010. One thing to note about Visual Web Parts in 2010 is that they will not work in a Sandbox SharePoint environment.
This link has a little information about Visual Web Parts.
John