I have tried whipped cream enemas and they are quite a sexy treat! Feeling the cream filling your rectum is very pleasurable. Shooting it back out of yoru ass is also a lot of fun!
The only thing you have to be sure about when using a pressurized can of whipped cream is that it is cold and that you keep the can angled down when discharging the cream into your asshole. If the can is not cold it will end up very liquid - you might as well be doing a milk enema instead. If you don't angle the can correctly it will just spray nitrous oxide gas into your rectum without any cream to accompany it.
From the first time I tried it I've been addicted to it. I fill up on whipped cream a few times a week now. I have a friend who likes ass play and we have a lot of fun filling each other's asses with whipped cream and shooting it out. I hope to post videos of that online one of these days!
So far I've never had any adverse effects from filling my ass with whipped cream other than a lot of "fartiness" from the nitrous oxide gas. The feeling of the cream filling you up can't be beat!
One final thing - a piece of rubber hose over the nozzle of the whip cream can can be helpful as the dispenser tip can be somewhat sharp.