Can I safely create new Virtual Machines from copies of VHD without sysprep?

If the same VM images are not joining the same domain and are within their own networks (unless you rename the systems), then it is not a problem.

You can, but it's not best practice because duplicate SIDs could create problems; however, if the machines are not going to be joined to the same domain, this should not be an issue.

Sysprep will not usually create problems to IIS, but you could run into troubles if you are using custom service accounts for application pools and anonymous access; it will instead create problems to SQL Server: http://blogs.msdn.com/b/boduff/archive/2009/02/12/why-not-to-sysprep-sql-server.aspx.