We use the built-in titler only for slates (for what that info is worth). It works well for this, and is faster to revise than an Avid slate, which is a plus as our slates get revised constantly.
For full screen text, lower thirds, etc. we have been using After Effects but are moving towards Motion. Maybe you shouldn’t have to go to an external program, but the round trip ability to open somethiing built in Motion from the FCP timeline is pretty powerful.
I’m also a little leary of programs that have “everything you need in one interface”. My experience has been that those programs tend to be limited in one area or another, and are much bigger and more cumbersome to load and upgrade. Think CorelDraw from 5-6 years ago, if you remember that…
tjs