Estudio or Estoy estudiando?
Lifted from a grammar site:
THE PROGRESSIVE TENSES
These tenses parallel English in form, but not in use. That is, people who translate directly from English to Spanish misuse or overuse this tense. The progressive is composed of a form of ESTAR or a verb of motion, and the present participle of the main verb, and emphasizes the ongoing or "right now" nature of the action. Observe the following examples: No puedo hablar ahorita porque estoy estudiando. (I can't talk right now because I'm studying.) La niña entró llorando. (The girl came in crying.) Los médicos aún siguen buscando la causa de su muerte. (The doctors are still looking for the cause of her death.)
The reason these forms are so often misued, especially with ESTAR, is because of the assumed one-to one correspondence between ESTAR and the English forms of "being--is, am, are, ...", and the present participle and English "-ing." Unless the ongoing nature of the action is being stressed, the indicative can often express the same idea: Saco mejores notas porque estudio más este año. (I'm getting better grades because I'm studying more this year.)
Not on this site. But I noted some interesting regionalisms in Argentina, where all they use for the future is "ir a +" and they --- like northern Spain -- rarely use the "he + past participle" as a past tense, using just the preterite. I was told in Mexico that over-using the progressive tenses with 'estar' was a big indicator that one was not very good at Spanish.