Prestashop = fail.
Avoid. It's in the same boat as zencart/oscommerce - less spaghetti code though, and they at least separated out some HTML from php. Except the developers don't fix things. And if you want any decent modules you're going to have to pay. And everything is in some weird french-english hybrid that will drive you batty when you're trying to fix a site.
It has an ok backend, frontend is god fucking awful to work with.
It's fine if you like to slam your balls into things and want a default template. Otherwise, use magento or a hosted cart service, or roll your own.
It's actually become my personal mission to warn people away from this software for any serious work. I really wanted to like. So much. Zencart and oscommerce are such turds programming wise, but so many people use them. I thought prestashop was going to be zencart but done right. Nope.