There was a question in forum list about how to get count of clients by its status (active,obsolete etc). I looked at it if there is any way to get it without report but No.
In Configuration Manager 2007,to know the count of Computers from collection,You right click on collection,click show Count will give us the information but in Configmgr 2012,this is not possible until you develop some custom tools to get this.By default ,You can only see the total number of clients Count and members visible but not how many active,obsolete etc .
I created simple report that produces this info.
Use the Below SQL Code to create SSRS report.
select fcm.collectionid [Collection ID],coll.Name,
count(case when fcm.IsActive=1 then '*' else NULL end) [Active Clients],
count(case when fcm.IsClient= 1 then '*' else NULL end) [Client Installed],
count(case when fcm.IsAssigned=1 then '*' else NULL end) [Assigned Clients],
count(case when fcm.IsObsolete= 1 then '*' else NULL end) [Obsolete Clients]
from v_FullCollectionMembership fcm,v_Collection coll
where fcm.ResourceType='5' and fcm.CollectionId=coll.CollectionID
group by fcm.CollectionID,coll.Name
order by fcm.CollectionID
Note:Change the quotes as they are not regular.