SSL - should I just make my entire site secured?
Solution 1:
There will be some processing overhead to establish the SSL connection, but on modern boxes and lightly loaded web sites that probably won't be very noticeable.
If you have forums where users are posting images sourced from outside your website, people will see an SSL mixed content warning (your site is SSL, but there are assets that are not SSL). Depending on your user population, that may freak out some people.