Answers to this your question break down along a few lines regarding opportunity costs of tying up a significant chunk of your salary and assets in one piece of property, as opposed to other things you'd like to do with your life.
The 30 year standard mortgage was invented in the 30's as part of FDR's new deal to make housing affordable to more people, while relieving the strain on the market of foreclosed homes from ~10 year interest only balloon mortgages (sound familiar?). The 30 year term tends to follow the career of the average American of that era, allowing them to pay the house off and live out the remainder of their lives there at a lower cost.
The real Value of a Home
Houses are depreciating assets because they wear out over time. Their greatest investment value is a place to live. The appreciation on a home comes from the real estate it sits on and the community the property is located in. Value is determined by desirability of the house and community in their current state, and the supply of property in the area. This value can only be extracted when you sell the home. This partially answers your last question noting that you shouldn't buy a really expensive building for investment value. We've learned in recent years that there are no long term guarantees of property value either, because land and communities can decrease in value due to unemployment, over supply, crime, pollution, etc. Only buy as much home as you will need in the next decade or so, in a place that you will like living over that time period, and don't consider it much of an investment.
Paying it off
I will tell you to get a fifteen year fixed rate mortgage since it's readily available at lower rates and has a significantly lower total purchase price than the standard 30 years. The monthly payment difference isn't that great, and anyone who looks at the monthly payment as opposed to the total costs, your priorities and the opportunity costs shouldn't be trusted for financial advice. I don't like debt. There are psychological benefits to being free from the bondage and drain of a long term mortgage on your finances.
The biggest argument for paying off your home quickly is freedom to pursue other desires with all of your salary and the assets you have available to you.
Some financial advisers will tell you to keep your mortgage costs under 25% of your income, so that you can actually live off the money you make. I would also recommend paying at least enough into your 401k to get the company match and fully funding your Roth IRA. I'd also have an emergency fund to cover at least 6 months of expenses, including this mortgage in case you lose your job. A 15 or 20 year mortgage will give you breathing room to take care of these other priorities, and you can overpay on almost any mortgage to decrease the principal and finish in a shorter time period (make sure to get a mortgage that allows prepayment) .
Diversifying into other investments
More financially savvy people may tell you to take the 30 year mortgage and invest the difference. Especially with mortgage rates around 4%, this is a very cheap way to increase your purchasing power and total assets. Most people lack the investment prowess and self discipline to make this plan pay off. There are even fewer guarantees regarding markets and investments than property.
This also is a way of diversifying your total assets to protect against loss of value in your home. This approach has backfired for thousands of people who are underwater on their homes. This problem is often compounded by job loss forcing you to move, or increasing your commute, making your home less desirable for you.
Some people will tell you to maintain the mortgage for the tax credit. This fails a basic math test since you only get about a quarter of the money (depending on your tax rate) that you are paying in interest back from the government. The rest of the money goes to bank at no gain to you. This approach is basically a taxpayer subsidized decrease of your 4% interest payment to a 3% interest payment (assuming you have ~ $5000 in other deductions), and only pays off if you can successfully invest the money at a rate somewhat greater than 3%.