Well, I think its key if you are going release any build it should be the best it can be and holding back on features for a later build may not get you the attention your game needs. Look at it as less alpha and more beta.

Having just opened the alpha version of my own game, I'm going through the exact same thought process.

The last project I worked on was a website where I took the opposite approach. I had an idea (it's a movie review index specifically for pre-1998 movies), then spent about 5 months developing it to absolute perfection. I showed nary a soul but I was really happy with the final result. I launched the site and a few people really liked it. The idea being the front page would be very clean and simple, similar to Grooveshark. Then about a month in I started getting feedback and every time it was the same response:

"Can the website be more like browsing a video store? Having a big search box on the front page is great and all, but I prefer just sifting through the movies rather than looking for something specific"

I'd built most of the functionality around the search interface expecting people to think "mmm, should I watch Gremlins? Is it still any good?" and go to the website and check. Turns out 2 people in the history of the site have used the search box on the front page. The rest just click around and browse around. This completely changed the way I thought people would use the site and meant I would have to do some really fundamental changes to how the site worked. Problem is after 5 months I was not looking forward to delving back into the code and I've put the project off ever since. The site just sits there now .

This could have all been avoided if I just got some feedback really early on! It might have looked horrible and only half worked, but getting that feedback at the start of the project would have been invaluable!

A case of this in action: My current browser game has a combat system and after spending weeks fussing over the most minor details and wracking my brain with ways to make it more and more complex, Acharis over at the game design forum posted "You are watering it down, these still do not focus on anything specific. These ideas could be a bonus, but not the foundation of a game". BAM! I realised I was going down the same path again - Planning a million ideas of what players might want, when all along they want something very simple and different. It definitely got me back on track and focused on what the game is about - Buying and selling parts to build up big awesome ships.

So, that's my spiel. It's difficult to show a work in progress, but I learnt my lesson. Get feedback early and often