All this talk about cantrip scrolls makes me want to post a little about the way scrolls look. I can't be certain, but I'm guessing most people imagine a scroll to be about the width of a tabloid newspaper, but instead of multiple stacked sheets, the sheets are connected at the top and bottom, with small rods attached to either end, so that when the scroll is rolled up, it's a tube a little over a foot long and about as thick as a half-used toilet paper roll. (Not the half that flushes...) This would mean that the incantation written on such a scroll would be rather wordy and should take a pretty long time to read aloud, unless maybe there are a lot of large magical symbols embedded in the text which the caster skips over during the incantation, but which magically glow as each is viewed. Perhaps a scroll of this size takes at least a half-turn to read/cast, making it impractical for combat casting, but fine for things like Knock or Wizard Lock?
In contrast, some people think of scrolls more in terms of a legal-size piece of parchment that's been rolled up. The text on the scroll is shorter and more reasonable for use at the beginning of combat, if not actually in the middle of combat; you could imagine such a scroll taking a single round to read. Also, it's much less of a burden than the other style of scroll. The "tabloid scroll" would probably be about as cumbersome as a dagger, but the "one-page scroll" would maybe be only half a pound. This difference in scroll models may explain why some people were shocked at Brendan's suggestion that 5 scrolls would weigh the same as 5 daggers; those people probably see the ratio closer to 4 scrolls = 1 dagger.
I see scrolls in a more extreme way, more like traditional talismans than scrolls. I think of a little square of parchment with symbols and names of power inscribed on it. The parchment is rolled into a small tube, sealed with wax, and an invocation phrase written on the outside. The whole "scroll" is no bigger than a finger, or one of those "horoscope scrolls" you can buy at grocery store check-out counters. The weight is negligible; ten to twenty of them would fit in a belt pouch and would weigh the same as a dagger. The big problem with such scrolls is not the weight, but the cost... and keeping them sorted so that you can find the right scroll when you need it. To invoke the power of this kind of scroll, I envision a magic-user reciting the magic words while breaking the seal; breaking the seal releases the power, and the magic words direct the power instead of allowing it to dissipate. A side effect of this viewpoint is that "talismanic scrolls" don't burst into flame or crumble to dust when their power is evoked; the seal can only be broken once, so there's no need for it to be magically consumed.
If you want to go the other extreme, think about sacred scrolls for various religions: rods about three feet long and long, long sheets of paper, with the whole think being about as bulky as a backpack. These are an armful, and are probably better suited as a model for alternative spellbooks than as individual spells. You could use this model for extremely rare ritual spells, though, such as if you don't allow memorization of 7th level or higher spells, but allow them as scroll items. Figure these would take one hour per spell level to read and may even require assistants to unfurl the scroll for the magic-user.
As you can see, the fluff surrounding scrolls can have a big impact on actual play.