I've only had my pre for a few days but I've been following precentral for a little while now. I know that Palm pays quite a bit of attemtion ot them. almost all of the apps in the official catalog start off as beta's in pre centras beta catalog. And I know thal almost all the patches are very safe except for those marked as dangerous.
Obviously its all beta stuff so it is at your own risk but overall its probably safer than installing anything on a windows phone.
I myself have installed a few apps and several of their patches with no hiccups.