For an Xcode project, is it good to add .xcodeproj files to the source control as well?

I am using Xcode 4.3.2 and realized that the project files are not added to the git repo, so I added them and committed: (there are 6 files)

# On branch master
# Changes to be committed:
#   (use "git reset HEAD <file>..." to unstage)
#
#   new file:   Proj01.xcodeproj/project.xcworkspace/contents.xcworkspacedata
#   new file:   Proj01.xcodeproj/project.xcworkspace/xcuserdata/jeremy.xcuserdatad/UserInterfaceState.xcuserstate
#   new file:   Proj01.xcodeproj/project.xcworkspace/xcuserdata/jeremy.xcuserdatad/WorkspaceSettings.xcsettings
#   new file:   Proj01.xcodeproj/xcuserdata/jeremy.xcuserdatad/xcdebugger/Breakpoints.xcbkptlist
#   new file:   Proj01.xcodeproj/xcuserdata/jeremy.xcuserdatad/xcschemes/FlipCard.xcscheme
#   new file:   Proj01.xcodeproj/xcuserdata/jeremy.xcuserdatad/xcschemes/xcschememanagement.plist

but is it actually a good practice to do so? (one time Xcode crashed and the folder .xcodeproj was gone).