We feel that pre-constructed tweets are downright lame; it's basically like saying "Hey, Mr Customer - we neither trust you nor value your opinion, but we want you to get your friends to buy our stuff anyway". Really old-school!
Cut the price, spend time advertising (through social networks)... jump 50 places all for free.
(Aside: Another thing that I can't check because I have no access to Itunes but a jump from say 1000-950 is not amazing neither is 700-650 so depending on where their app is placed and how many apps there are I don't know that this means anything.)
I understand your concerns here. Fortunately, the features users receive are permanent (for a given install) and we allow free-form responses (some guy actually wrote "Tweeting for upgrades sucks" in order to get his upgrade - and we're totally cool with that).
Mostly importantly, it's been a really interesting experience in metrics, marketing, user feedback etc. Not an especially profitable one, but valuable in our understanding of how this sort of thing can work.
I think what's against the app store terms is to show disabled features that are only available in the paid version of an app. (which Apple has done for years in QuickTime ironically)
This probably falls in a grey area: if you compare it to game levels that are only activated after you achieve something, it's pretty similar in spirit. Now that I think about it, I think some games are borderline then…
I hope the MacHeist bundle people can learn from this.
Sending pre-constructed tweets is more like network marketing (alienate and/or annoy friends) than word-of-mouth.