For most forms, optimistic locking is the preferable setting, because it keeps records locked for a much shorter period of time.
You need to think long and hard before you try to get into the locking management business. NO WAY can you handle this better than Jet and ACE. Plus, if your table is some other RDBMS, you cannot use Access lock settings to manage locking anyway.
With optimistic locking (the default) each record is locked only long enough to effect the change so it dramatically reduces the potential for contention even in a busy application given the blink of time the update actually takes. With pessimistic locking (Edited Records - what you are using), the record is locked as soon as it is dirtied and it
STAYS LOCKED UNTIL the user saves it or uses esc to back out of the update. So, if the user is interrupted by a phone call or the siren call of lunch, the lock could persist for hours and could even block a backup if left overnight. At best, the lock will persist for multiple seconds at least and probably minutes rather than a microsecond.
If your form shows the RecordSelecter, there are three icons:
1. Right triangle - current record (only relevant on a continuous or ds view form)
2. Pencil - record is dirty (ie being edited on THIS computer)
3. Circle with line - record is being updated by a different user.
When a user sees the Circle with line, he should NOT modify the record at this time. But even if he doesn't, he could still get an error message. Assuming the first user committed his changes, the underlying data on the server has now been changed and therefore, the values the second user is seeing might have been changed by the first user. Therefore, if he now makes a change and tries to save, he will still get an error because there is a conflict. The message is confusing and gives three options. You need to train your user to simply back out of the edit and try it again. This will retrieve the current column values which might be different than they were a few moments ago.
The most confusing situation is where UserB is is faster than UserA and saves first. UserA never saw the locked icon and so is surprised by the error when trying to save. Anyway, there's a limited number of situations and you can create screen shots and displays of the messages along with instructions and it will be safer and easier than trying to manage record locks.