Wasn't there a successful client on Windows 8 recently, a platform where there wasn't even an official client, and they refused to forgo the API limits on the number of users you can have?
Using the Twitter API is setting yourself up for failure.
Most companies turn kind of hostile with their API when money is at stake but Twitter has been particularly bad, especially considering a lot of the innovation on their platform happened on third party clients. They haven't mustered any kind of innovation of their own either.
The Chinese weibo's like Sina are actually quite a bit more interesting if you can deal with the language and the governmental interference.
If you want a ground floor learning experience app.net is probably a better choice though I doubt its ever going to gain critical mass.
"A developer should never trust an API or expect anything of it if he's not paying for it. As long as you're not paying, you're just another developer to the API provider. The moment you fork over any cash, you're a customer."
Mind, this is really crudely paraphrased, but the sentiment remains. This was immediately in the wake of Twitter's API changes last summer.
I mean, either you develop on Twitters API or you have a gaping hole in your social media analysis product... Game over?