[Zope] Limitations of just using External Methods ?

[chas]

Hi zoppelgangers,

I have several applications built 100% with python CGI
scripts that I'd like to run on Zope. The reason for 
this are :
a) For the better performance (I was worried about
   the scalability of CGI for high-availability and
   knew I had to move to FastCGI or the equivalent)
b) I really really like the way Zope takes care of
   the CGI variable handling (ie. declaring the 
   HTML form fields as arguments in the python method).

However, I don't really want to use DTML at all.
The reasons is that I find it much harder to read 
than pure Python. This is just a personal aesthetic 
thing and no criticism of Zope at all (full kudos to
Digicool on an excellent application). It's just
coding aesthetic : I like it all kept in Python, 
like servlets in java (as opposed to CFML, ASP etc).

So, I've put all of my CGI scripts in a newly-created
extensions directory and registered them via the 
Zope web-manager. It was, as the documentation says,
incredibly simple and it seems to work for simple
methods. (I'll declare my own packages later).

Now, if I just use External Methods like this (using my
own ex-CGI Python scripts to query databases, IMAP etc),
am I missing out on any of Zope's main benefits ? 
In particular, the cache management ?  
Would I have to turn my stuff into  a Zope Product to 
get these benefits ? (I've not had too much joy with
the Product stuff yet)

chas