I'm currently playing a runecaster (Clr 6/Rnc 10) and i don't use the runes very often (at least not as often as i thought).
One of the reasons i don't to use runes is because it's really expansive to create high level ones. Usually i carry one word of recall rune and several maximized lesser restoration runes.
I only inscribe runes on small metall plates or stone blocks (meaning really small, the size of a d6). My armor is covered in runes but only non magical ones, mainly because i'm not really sure which rune to use. Harm is a good one if you don't want to be grappled but there is always the danger of your alies touching you.
PC1: Hey buddy, how are you (patting me one the back). .......Gah i'm feeling "really" weak.
ME: Yeah great, you just wasted 3300 pieces of "my" Gold (not to mention the XP). (sigh) Need some healing?
PC1: Um.. yes.
The "space limitation" (one rune on medium size object) isn't really an issue because you can easily strap small metall plates on your arms (with the help of some leather straps).
Additionally most armor consists of more than one piece, so you can write 20+ runes onto your fullplate.
On the topic of permanent runes i have to say that i personnaly haven't created much of them (detect magic and detect evil). You better stay away from perm. (maximized) cure runes (unless you want to feel the wrath of your DM). Although you could write 160 scrolls for the same cost (it's only more time consuming) most DM don't like those permannet runes.