Ask HN: ComboApp, GTekna, are they worth it?

I know this question is very likely to make an outcry but I still would really like to get some input regarding "App marketing agencies" (as they define themselves) like http://www.comboapp.com/ and http://gtekna.com/.

I'm about to release my first own app in a few days (http://www.waitapp.net) and although I'm fairly proud of it, my pride isn't going to do anything to promote it. Services supposedly provided by those "agencies" are pricy but so are in general marketing and promotion efforts when related to more traditional products and still quite necessary when you want to bring your product to the public eye.

Once again, I'm fairly proud of Wait, my app, and I believe it stands a good chance in front of other iPhone timers, but I can't rely on an hypothetical AppStore promotion, and I still need at the very least to jump start the word of mouth.

Unfortunately, an app, regardless of how good it is is as good as dead if nobody knows about it.

So, yeah, is it worth shelving a stupid (maybe) amount of money with those agencies?