Over a year ago I wrote an article here on Medium going into some of the initial challenges I had working with dynamic text in my first iOS game phobium. The game was essentially a native mobile version of my first game Raid Encounters that allowed me to expand on some of the things I wanted to do with a ping-pong style game like that.
SpriteKit is something I heavily use in my projects, even the upcoming 3D KOZMONAUT and at times you need to know its limitations and how to finesse it (which I'm still learning about now). The article goes into utilizing bitmap fonts and I ended up converting the entire engine to using them. As of now, bitmap fonts are not natively supported by SpriteKit but there are a lot of nice implementations out there.
If you're interested in that sort of thing, go give it a read!