When picking users in collaboration studio, you need to type the from the beginning of the user name. When using AD integration, you need to type the domain name first to start filtering on users.
I would like to have the option for a free text search on the email, user name and some other user field that might be attached to users.
This works (partly) on the System user search window, where the search finds also matches on the email address.
Customer support service by UserEcho