About 2 years ago (soon after Drupal 7 was released), I had a site with a number of fields attached to a content type. When I had to clear caches and reload a page, it would take an awfully long time. This is because the site would need to run load each node, run a query for each field, process it, and more. What was good, though, is that all of these fields would then get placed into the cache_field table so the node could load faster on subsequent loads.
Thanks to some of my projects being completed ahead of schedule, I was able to go to the Drupal Meetup in Santa Monica (LINK) last night. John Romine had a question for the community on how to alter one of the fields in his view to render the way he would like, Jeremy Stoller went about it by doing things at the theme layer while I (as usual) approached it by doing this at the module layer (depending on what you want to do, either way works).
I am a big fan of the Display Suite module. Its quite flexible and gets you up and running with a look/feel fairly quickly. One of my favourite features of Display Suite is that you can create various build modes so that they can power your views or results or have then get used in a various areas of your site. Find out how I keep things speedy through the use of the Entity Cache module with Drush.
While working on the one of the more content-heavy websites at my workplace (over 100k nodes consisting of galleries of photos, with some galleries having well over 2000 photos), I had noticed that while performance for logged in users (which isn't high since only site editors can log in) has mostly stabilized (there are areas where performance can improve), performance for all other site visitors was very inconsistent. Some of the galleries and gallery photos pages seemed to load fairly quickly while others took a few seconds for the page to show up.
I have the pleasure of working on CalArt's Photo Archive. From the conversion as a flat-file website into Drupal, the site has come a long way. And for a mid-sized website (a little over 100k nodes) running on somewhat older hardware (at least 3 years old), we are fairly happy with the performance (using the boost module allows us to serve cached content at approximately 2k requests per second). However, I was noticing that some of our content type pages were loading quite slowly prior to being cached.