The little spider things are very much like the requisite evil-esque species. Even though they blow up easily, they're supposed to be a menace because they attack in huge numbers, obsessively create more of each other from whatever they can find, and methodically overwhelm and kill whomever opposes them. They apparantly have destroyed hundreds of civilizations and all that jazz. Even though they're easy to kill individually, there's usually so many of them that attacking any is suicide, since there's no way to destroy them all. The human ones were pretty much sentient, "evil", and unstoppable before O'Neill came up with that weapon.
It was odd that Teal'c was able to beat them so easily on the Asgard ship. I guess their main mission was to get Carter.
Anyway, I enjoyed it.