I also bought a new memory card, a much faster one. Now the 7 frames / second burst mode takes 5 seconds instead of 9. I was using a class 4 memory card before and now I have a class 10 which writes as fast as 90mb/second.
Which makes me wonder why it takes 5 seconds. If each picture is about 3.5 megabytes and we multiply that by 7, we get 24.5 megabytes...let's round it off to 30 megabytes...per second. So in theory even a 30 mb/s memory card should be able to handle these pictures in one second. Why does a 90 mb/s take 5 seconds?
The key word is 'as fast as', which means it might achieve that speed when the planets align just so, but otherwise not.
The card speed ratings are painfully optimistic in most cases. The professional grade cards which carry huge price premiums have more realistic specs and often guarantee a minimum speed. Also note that there are different read standards, most with lower maximum speeds, so the camera may be limiting the throughput, not the card.