Judging from the images published on various forums displaying X-Plane screenshots, it seems that most X-Plane users click the checkbox opposite Frame Rate in the Data Output tab in SETTINGS, a frame-rate display appears, and because it is fairly unobtrusive they seem to forget about adding any other monitoring readout. It is a very good idea to periodically look through the list of items that are checked – particularly as you learn more and more about X-plane – and re-assess what should be displayed.
For example, an old joystick or yoke can drift out of calibration more often than you might realize. If you add a check in the box next to Joystick aileron/elevator/rudder (Index #8), a glance at it while flying will re-assure you that your main flying controls are working to the full extents and not require re-calibration.
Spend some time browsing the list of what can be displayed in flight – you may well be pleasantly surprised.