Being an ACT user since version 1, my comfort level is more with the keyboard than with the mouse for expediency.
To that end, when adding a contact to an opportunity from the Contact Detail screen, there are two problems:
1. Type ahead is active, and I haven't found a way to turn it off. The lookup will probably display the wrong opportunity if the user pauses. The opportunity that displays is the first on in what looks to be alphabetical order. For me, the system generally finds the incorrect opportunity. In other similar dialogue boxes, such as the "Attach to Act! Contacts" from within Outlook, type ahead is active, but the highlighted data is replaced upon the next keystroke. The result is that the user has time to enter the lookup string.
REQUEST: Remove the type ahead feature or make it work like "Attache to ACT! Contacts" as used in the Outlook plugin.
2. Having detailed the issue in #1, a work around is to use the down arrow to find the desired opportunity, and then press Enter. When the correct opportunity is displayed on the screen, only the OK button is highlighted that when pressed will not add the opportunity to the contact - in essence under these circumstances pressing enter has the same effect as clicking on Cancel.
REQUEST: Add the Right Arrow ( > ) to be highlighted for the Enter Key when the correct opportunity is displayed.