The potential problem is that “easy” is relative, and “easy” does not necessarily mean “secure”! Many, if not most, of the PHP “formmail” scripts readily available on the web are inherently insecure, and can be exploited by spammers to send spam.
I don’t know about the one you are using (and don’t really feel like reviewing the code to see!). The DreamHost script is pretty robust (a modified version of the perlmongers NMS formmail script) and DreamHost feels it is secure enough to make it generally available.
Do you really want to get a contact form up “easily” only to have it used to send spam? Wouldn’t it be better to spend a little more effort getting it done in a secure manner?
If you provide the link to the “generator”, I’ll take a look at what you have to do to install the produced form, but I don’t want to vouch for it’s security!
Alternately, there is additional help on using the DreamHost fommail script in the DreamHost wiki. You might take a look at that, and see if it is helpful to you in implementing the DreamHost formmail script on your site.