Changes I'd like to see:

(1) Hotkey functionality and a better menu location. The odds of me finding this without the patch notes handy are quite low, and for people coming into the game later, they may likely never discover the system exists.
(2) Permanence. I do appreciate the macro command presented to us, and I realize that macros can set the alarms back up, but this is far less convenient than running Garland Tools in the background.
(3) Alarm 'sets' allowing us to turn groups of alarms on or off quickly and easily. Again, I point to Garland, where one can create a series of tabs, and only the alarms on the current tab are active.
(4) The ability to set multiple times for the same alarm. Most Gathering nodes, as well as Gold Saucer GATEs and the like, occur multiple times per hour. Right now I'd have to create three separate alarms to cover the Gold Saucer GATEs. I should be able to create one, and have it repeat on adjustable increments rather than just hourly.
(5) Higher number of alarms permitted. Honestly this entire system should be running client-side with the game simply providing an interface; given that, we should be able to set as many alarms as we'd like, since the servers should have no role to play.

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It's a good start, to be sure, and a particular boon for console players. For PC players, however, it's still a poor imitation of the alarm systems offered currently by third-party sites and databases. Adding in those changes I suggested would be a good start toward bridging the gap. There are still certain aspects missing that may or may not be feasible to implement in-game, but at the very least, SE should work toward building some of the more fine-grained functionality offered by common reminder systems.