I have one dedicated server with Windows 2008 R2 Enterprise. I need Web, SQL and Services servers. Is it good idea to use physical server only as Hyper-V manager and for each specific server use one Virtual VHD?
Definitely - especially for development and test. Hyper-V allows you to snapshot, roll back, have people self service new instances when they need it. Especialyl those doing installation tests may appreciate this - I definitely do.
I personally am retiring all physical server usage with some exceptions (utilizing a physical server as file server, domain controller) and put everything else on hyper-v instances since hyper-v became available. Never looked back - things just are easy, including hardware upgrades (install new server, move servers, no need for handling driver issues).