One of the great features added to ACT a long time ago is the ability to reassign a history entry to another person, group, company, or opportunity.
I think I've mentioned this many times before, but when I'm assigning a history item in a contact's history to an opportunity and finally get to entering the opportunity name, the cursor highlights the entire name of the first one it finds from the typeahead feature instead of allowing more characters to be entered. By being fully highlighted, the user assumes that is the opportunity when in fact it isn't. They then give up on this feature and assume ACT can't find the right opportunity.
In the above example, the user wanted "Citrix XenDesk" Once "Ci" was entered, the first one was completely highlighted. The user stopped looking further since it could not be found.
I know this seems like a simple matter, but not all users are technical. The one highlighted is not what they want, so in this case, the reassignment is abandoned.