If you follow online Flash games at all, you may have noticed a new Pokemon Tower Defense game recently. Honestly I forget when it first appeared on the Web, but it's been around long enough to amass a pretty significant following and appears destined to become quite popular, if it hasn't already. (The developers do have a blog, of course.)
I have to say, though, I think my first reaction to it has colored a lot of my personal opinion on it since. And I'm not ashamed to admit that that first reaction was generally negative. Really, the first blow was struck when I reached the game's main menu, only to find the majority of the options grayed out with the note "will be added in the future". And when I went into the story mode, only to find no more than three levels and another "coming soon" note? Yeah, that didn't help matters.
They've been good about updating it fairly regularly since then. The v2.8 that we're at now has a lot more than the original did, and their blog has detailed notes about future updates. And considering the popularity of the game, I can't deny that it's all working out quite well. I just don't really think I like dealing with a game that's still in alpha.
I would think that most gamers are well familiar with the idea of a beta version, considering how common open beta tests are becoming these days. The concept of the alpha version, the version prior to the completion of all features in game, is probably less well known considering that (as far as this Wikipedia article is concerned) "external availability of alpha software is uncommon."
Perhaps the age we're in is going to change that... but then again, perhaps not. I can only speak for myself, but I can say that I'm not a huge fan of dealing with a game that has so obviously and clearly not been completed yet. I can see making balance adjustments, bug fixes, and even significant upgrades to a completed game; I played in the Starcraft II beta after all. But handing me 5% of a game and telling me "hey, check out this new game I made!" strikes me as somewhat disingenuous. You don't have a game yet, not by my definition of the term.