Any downsides to installing suPHP?

For an ecommerce site...

[Wlauzon]

Setting up an ecommerce site on a VPS, and the hosting company says I should have suPHP or some other suEXEC compiled with Apache to keep the cart program recommended file/directory permissions of 644 and 755.

It seems to me that is the way most shared hosts operate by default - is there any downside to it?

Otherwise I will have to change all the permissions to 664/775, which does not sound all that safe for a supposedly secure site.