[MENTION=6802559]ryan92084[/MENTION]
You know, on reflection, I think you have an interesting point. Either all of the spellcasting fiddly bits are done and the effect is in place but being held for later release (meaning there's an effect hanging out) OR you do most of it during the action but there are still some parts that need to be finished later, in which case you're technically not done casting until the release. (There's a third option, where you fully cast the spell, concentrate on the not there spell/effect for a bit, and then release the no actually there spell later, with absolutely nothing in between the action and the reaction, but that's boring).
In the first case, it would make sense that dispel might work, because you're literally holding the effect of the spell for later release, but could only counterspell on the initial casting action. In the second, you couldn't dispel, because there's no effects yet, but you could counterspell -- when? That's a bit more vague. I'd definitely say on the release, and probably on the initial casting action, but maybe even in between?
Nifty. I think, though that the rules favor the first explanation more than the second, due to the wording 'cast the spell as normal.' So, you're either holding the finished effect for release* or you're holding a not spell/not effect.
*Huh. Casting the spell 'as normal' would imply that you go through all of the steps, yes? If that spell generates attacks, would you not then also choose targets, but without the resolutions until the effect is released? Nope, in thinking, the attacks are the effect of those kinds of spells, so releasing the effects would generate the attacks then, not during casting. Please ignore this stream-of-posting thought.