Two months back I launced 3 new Drupal-7 based sites on my shared hosting account but soon I found that my account was touching maximum process limit of 25 in my account and that my D7 sites were having only 400 or so page views daily. To compare it with D6 site, it could handle 4000 pages views without any problem.
Hostgator support confirmed too many processes of D7 sites. I've also checked it and I find that D7 index.php is running for much more time than D6 counterpart. So instead of it exiting in .5 second, I guess it's taking 3 seconds( rough estimate). I don't think those are eating too much of CPU in that case my sites would have been suspended.
To resolve it I'm moving my D7 sites to VPS so that process limit is increased.
I'm using all Drupal default install settings. No booster etc modules.