The biggest thing I miss using easy projects that I had in MS project is the auto calculation of lag times. If you have a task with a five day duration and the next task is dependent on it finish to start also five days. The 2nd is lagged to the 1st by 5 days. If I want the 2nd task to start 2 days earlier you currently have to change the lag time from 5 to 3. It would be extremely helpful to be able to change the start date with the calendar pick to two days earlier and have the lag auto change from 5 to 3. Also, if you wanted to set the finish date on a task it would change the lag the same. The other related would be to assume the duration is the driver. In the example above, if you wanted to move the finish date of the 2nd task 8 days earlier it should drive the lag time to a -3 and the start and not move the 1st task.
We often have tasks that we don't change the duration and you want to move out two weeks. It is a pain to change the lag time multiple times to get the finish date to show up where you want it.