The 7D still is a great camera. However, ISO wise it is really no better than any other current 18MP APS-C cameras - even the Rebels. The key to having less noise in your high ISO shots is to have good light. In poor (low) light, ISO 1600 will look noisy on a 7D. With better light you can go up to 6400 in a pinch and it may look OK. Just don't try using 6400 in very low light as the noise will be very bad.
In terms of comparing it to your 30D, try this site: http://www.imaging-resource.com/IMCOMP/COMPS01.HTM
It allows you to compare different models side by side. Just bear in mind that these are studio shots with good light so it makes it hard to see huge differences.
Handling wise, you will definitely enjoy the 7D over the 30D. Almost everything about it is a vast improvement.