My original plan was to pay $1.00 for this game and then boost it when it's released from alpha (Since I despise paying for games that get stuck in pre-release with minimal content being added.  Looking at you, Minecraft and Terraria).  Once I got into Amazon I went back to the Humble page to change the setting to all of the money going towards Voxatron and forgot it resets the price to $29.99.  So I just paid $30 bucks for a game that I finished in an hour.  Since I know that refunds do not happen, I hope the massive amount of money I just gave you (In respect to time invested on my part towards completing it) helps to fuel this into a game that is open ended and refined enough so I can sink in plenty of hours later.  Played great, I loved adventure and the really cool monsters, would love to see multiplayer and a hundred times more content.
dude.. just use the instant chat with support on the humble bundle page...
There is a chat window that you can pop open on the bottom of the screen saying "Chat with Humble Support".
Try to get your money back that way, it might help, and will help better than trying it here on this forum...
good luck :)
Edit: P.S. I'm not the developer or anything, just a random guy giving some advice..
Also, you might need to wait for about 5 minutes before you get a reply, but the humble bundle support team is VERY helpfull!
Hey now - Minecraft got stuck in pre-release but there's still a pretty good flow of new content! One of the advantages of pre-release is that a modding community can develop. I think that most of Voxatron's appeal will stem from the community's additions, which is what happens with Minecraft, too, now that I think about it.
I don't doubt that Voxatron will come to state that worth more than 30 dollars or you'll get the enjoyment out of it. More community maps and you'll be seeing hours pass, I'd say!
Moreover, overpaying for Humble Bundles ("overpaying", I should say, with air quotes, because we all know this game is priceless) is a common thing and their support should get you figured out if you really need your 29 dollars.
The "new" content is too often material that the community already came up with, so I see absolutely nothing I haven't before.  If he released the game, supported modding and enabled it in multiplayer he'd have my entire support as that would allow the biggest amount of new content I could possibly imagine.  As it stands, it's ridiculous trying to get the game to play how I want and needing a boat load of bukkit plugins.
If most of Voxatron's additions come form the community and community made additions are SUPPORTED, then heck yeah this game could flourish like no other.  Games that are simple at their core but allow for ridiculous amounts of expansion make for games that are easy to boot up and just waste HOURS in as, at their bottom line, it's just simple fun.
I talked to support and they sorted it.  They were super helpful and I'm really surprised.  I'm not saying this game is bad.  Far from it.  It was really enjoyable and I eagerly await new content.  However, at the moment, the amount of time I can put into it versus what I'll pay is minimal.  I'm not paying to get something in the future.  When it arrives, I'll boost what I paid.  I hate stealing games.
With a monster editor being planned (and I'd assume item editor, etc...) you're going to have a pretty open way for people to edit mobs and items, as well as maps, and that'll all be integrated into the game and supported!
One of the things I look forward to is demakes of old NES top-down games. The engine's potential is great, and the fact is, most of the content will be user-generated. That's why there's a link to download more maps built in to the game already!
See, I love NES and SNES games.  I can boot them up, no waiting around, no mindless traveling, no waiting to respawn, it's just fun fun fun.  And this game is like that!  And once some awesome lengthy maps are released I will be ALL over them, as well as the monsters (Of which there are already a super surprising variety!  I was REALLY impressed, guys!  The disk throwing ones are suuuuper cool!) and items.  I just don't like paying for content that isn't here, yet.  That's why I had hoped there was a demo. xD