Yes, I'm glad that I'm learning so much everyday vocabulary, but what about the verb tenses?
After studying Spanish for weeks on end, I can't even bring my self to say "I learned Spanish on Duolingo."
Well, of course, you can't say 'I learned Spanish on Duolingo' since the first time you'll encounter the Past (Preterite) is in about the last lesson before the last shortcut :). But from then on you'll get Phrasal Future, Present Perfect, Past Perfect, Future, Future Perfect, Subjective, Imperative, Conditional, Imperfect, Subjunctive Past and Conditional Perfect.
I know it is frustrating right now but I think that, from a didactical point of view, it makes sense to postpone the introduction of other tenses. Now you can focus on grammatical concepts and word order without having to worry about lots of verb conjugations :) .
Of course, you can always go to Wiktionary, Spanish.About.Com, WordReference etc and look up the conjugation if you want to say 'Aprendí el español en DuoLingo'. Replacing one tense with another will usually work. :)