What API do people use for bitcoin market data?

[BillN]

I am developing a website that does some things with the BTC exchange rates from different markets.

I was wondering what the general best practice is under bitcoin related website developers. Do you guys use the bitcoincharts api since it has data nicely formatted for all markets? Or do you guys use each markets individual API?

Any ideas about the pro's and con's of both?

Using bitcoincharts:

pro:
- only one API to call
- returned data for different markets formatted all the same

con:
- only 1 API call in 15 minutes

Using individual markets' API:

pro:
- call rate more often than once in 15 minutes

con:
- multiple API's to call and build code for
- different formats of data returned

How reliable is bitcoincharts -- I would like to use it but feel that they can shut down and I will have to build something for all markets still.