I depends, if you are looking to establish a brand then the domain name is important, otherwise for the usual content sites, I will not make much of a difference
well ,it does worth buying...because if you are planning to do something..eg: establishing a newspaper or ad film making company then you must have everything perfect according to your need...including domain it doesn't matter how much it costs you...
A premium domain is a domain that has been registered previously and is back on the market for resale(it’s like a used car lot for domain names … but these items have not depreciated in value — in fact, it’s quite the opposite situation). It is worth yes but it is hard !!
If you can find a good domain name that's unique and fits your site better than any other - it may be worth it in the long run. Especially so if you have corporate $$ backing you ;)