Here in Colorado it's very informal; it's just not the norm to wear a suit to an interview. It raises eyebrows. This is especially true for tech jobs. I would never not hire someone because of this, but the reality is I've never met anyone that over-dressed like that for an interview that aced it. If they did, I'd probably joke with them about the suit, but that would be that.
I also personally find suits unoriginal. It's actually more work to find a nice outfit that is stylish, professional and looks good; a suit is like choosing Pad Thai at a Thai restaurant - it's just the easy choice, not necessarily the best choice (though sometimes it is the best choice too). I also think ones appearance gives you a glimpse into what makes them unique; if I'm meeting you to consider hiring you then your appearance matters. It won't be the reason I hire you, or not hire you, but it matters. Sorry if that bothers you.
I guess I'm just confused now. What would you wear that is stylish and professional that is not a suit or a derivative thereof (collared shirt, wool/linen trousers)? You ruled out about 90% of a professional's wardrobe, as I see it.
When attending an interview, I want to look smart and make it clear that I made some effort to dress well without trying to stamp my personality all over people, so the default choice is a well-fit suit with a nice shirt. I'm genuinely curious: what would you wear, or expect someone else to wear?
I can only speak for myself, I don't expect anyone to dress a certain way (beyond what has been covered - aka a suit is over doing it, trying too hard). But me, I typically wear a pair of nice dress paints, let's say charcoal gray. I'd pair that with a button down dress shirt, long-sleave - something that is s solid color, usually a bold choice there to stand out such as burnt orange or a burgundy for example. That's pretty much it other than of course matching a proper belt and shoes (in this case black shoes and belt, I'd go to Aldo's for that). Just swing into Banana Republic or Limited for Men; poke around those shops and you'll get the hang of it. Maybe pick up an issue or two of GQ and Men's Health while you are at it. You can also switch out the long-sleave shirt in the summer for a shirt-sleave polo style shirt; I'd again get something more modern from a shop like Limited/BR, but you get the idea.
Anyway, that's literally what I wear to work most days. I have 3-4 pairs of dress slacks from a good store like those, different colors - black, charcoal gray, dark brown and a light gray (almost a tweed). Then you can buy a variety of different colored shirts. Then you just need a pair (or 2) of black and brown shoes, and matching belts (though you can probably get away with black shoes, and a black belt with the brown slacks, but I personally like to really look 'compete').
It's funny but I was starting to think about creating a post or blog entry on this because it's not that hard to dress really sharp without going too far. Also, if you aren't good at picking clothing bring a girl with you, or just ask one of the store clerks, they are usually really into this stuff and can point you in the right direction (but always pick things that appeal to you in some way, allowing them to influence your choice, not make it for you).
Strikes me that the only difference between the way that you and I dress is that I wear a jacket ;-) (I can't stand ties). I wear the jacket because the silhouette is flattering, and there are all those handy pockets. Why should such a simple, very practical item make you think at such a person is over-dressing?
I also personally find suits unoriginal. It's actually more work to find a nice outfit that is stylish, professional and looks good; a suit is like choosing Pad Thai at a Thai restaurant - it's just the easy choice, not necessarily the best choice (though sometimes it is the best choice too). I also think ones appearance gives you a glimpse into what makes them unique; if I'm meeting you to consider hiring you then your appearance matters. It won't be the reason I hire you, or not hire you, but it matters. Sorry if that bothers you.