I said "Sometimes", but really, it sort of depends. In low-level games, it's rare or never -- you just don't have enough 2nd level spells to go Stilling a first-level spell for that slot unless that's your whole gig, doing the (non-3.5 bard) armored caster thing.
At high levels, my guys were always tossing around metamagicked whatsits of lower level stuff.
And random side-note: Had a ton of success with a d20 Modern one-shot wherein I collapsed all magic to work as follows:
- Each spell you get costs you a feat.
- Casting a spell is a knowledge(arcane) check
- You can do a lot of things to modify it, such as lengthening the spellcasting process to a full minute in order to make it easier, shortening it to a standard action (from a full-round action), which makes it harder, or stilling and silencing it.
The more d20 stuff I play, the more I love the core "roll d20 and beat DC to do what you want" system. I wouldn't make every spell cost a feat in a D&D-type game, but you could do it with something like "Mind Control Magic" as a feat -- Charm Person is easy, Dominate Person or Hold Monster is hard, Dominate Monster is next to impossible.
Random thought, sorry for topic drift.