The value is in Bitcoin the payment network.  Every time a new merchant adopts bitcoin or another service is created to be layered over the protocol or the current network attracts another hour of development time or dollar of venture capital the payment network of Bitcoin increases in value (both "real" and speculative since increased "real" value ought to beget more of the same due to the network effect and as such has an attached speculative value as well).

The bitcoin "coins" have a value because they are the only allowed units of account for this valuable payment network and they are predictably mathematically scarce.

It doesn't matter whether or not you see value in this network.  There are countless things in this world that I don't personally value at all, that if given I could sell and therefore have value regardless of my feelings or anything else.

This is why copying the source of Bitcoin as BitcoinClone won't immediately give a valuation of the BitcoinClone units of account the same value as those of Bitcoin even though the technology is identical.

Hopefully this gives you some insight as to why bitcoins have a value on the marketplace and why altcoins don't make Bitcoin completely "redundant".

Much of my verbiage has been stolen from Erik Voorhees.  I think his method of explanation for Bitcoin's value proposition is concise, effective and easily understood for those who don't see it for themselves at first.  For me the value of a widely established p2p decentralized digital payment network was obvious.

Here's an example of his explanation with more detail if interested:
http://www.reddit.com/r/Bitcoin/comments/1rxmk3/my_open_letter_to_peter_schiff_followup_from_the/