I think it's great! Although I haven't used a flash card app before, so I'm not sure how qualified a judge I am.

My only comment is that on screen widths between about 780px and 1200px, the text and fields in the two side widgets of the main flash card view overflow from their white backgrounds.

I like it, I clicked on US State Capitals and it started a card. My first thought was "I don't know many US State Capitals, how do I see the entire list to get started". So perhaps add a way to present all the info in a set so a learner can quickly be exposed to the "question/answer" pairs before actually being asked to provide answers.

Also, not sure if it was something I did, but after I cancelled a session, I could no longer start a new card set. I'd click them and they'd go into "my decks" but clicking the deck would only launch a context menu thingy to edit the deck properties. How do you run them?

> I'm building general-purpose spaced-repetition (flashcard) software for the browser:

Me too! But I'm at pre-alpha. I'm using asp.net mvc & knockout.js

Looks great.

I signed up and tried to create a new deck to study as a test, but that doesn't seem to work yet?

Looks nice, I submitted some patches to a similar project a few years ago (Mnemosyne, Python+PyQt). What algorithm are you using for scheduling the repetitions? The unmodified SM2 or Anki's derivate of it?

Incredible! I feel like meteor is so unbelievably perfect for this.

Feedback: once you've clicked on a deck, there's no way I can see to get back to the home page as shown when you refresh the page.

It looks well done. How was it with deploying Meteor on Heroku?