Views vs Performance
Performance is very subjective and varies widely from site to site, depending on how much custom code you have, how many logins you have, and what your expected usage patterns are.

The first thing you should do is figure out what your expected usage patterns are going to be, put them in a spreadsheet and estimate how many concurrent visitors you'll have on various pages, etc (for example, how many logins will happen at one time, which pages have the highest traffic, are your users authenticated or not).

The second thing you should do is prepare some kind of load test using something like LoadStorm, or even something very basic like JMeter. Set up some scenarios that mimic or exceed your expected traffic patterns. Then run the tests.

When you start load testing you will very quickly see where the bottlenecks in your site are. You can take cachegrind dumps of your site while you are load testing to see where the performance bottlenecks are using the XDebug profiler. You can also watch your database performance (CPU/memory and disk I/O are easy things to keep an eye on).

Once you've done all that, you can look into the following:


PHP opcode caching to speed up your web server
A reverse proxy like Varnish to take some of the load off 
Setting up memcached to take load off of the database
Tuning the database
Setting up load balancing with multiple instances


Drupal has a decent listing of caching modules/options and how they perform for authenticated and unauthenticated users here.