That's quite correct, of course. Still, you can write puhekieli (as most of us do daily in informal textual communication such as IMs) and it's still very close

That's quite correct, of course. Still, you can write puhekieli (as most of us do daily in informal textual communication such as IMs) and it's still very close to phonetic, although there are individual differences in how "spoken" and dialectical their written puhekieli is. Some common puhekieli traits like the widening of the diphtongs "uo" and "yö" to /ua/ and /yä/ are more rarely reflected in informal writing unless one wants to specifically underline or exaggerate the pronunciation (eg. for comedic effect, or in written fiction featuring persons speaking a dialect).