I have been using Drupal since version 5, and I am very concerned with Drupal 7s performance on shared hosting. There are numerous post on Drupal.org and elsewhere on the web where people are expressing concern about Drupal 7s performance on shared hosting. If you google Drupal 7 performance, the majority of the results lead to negative reviews of how Drupal 7 performs on shared hosting.
The clients I work with are small businesses and need to start out with shared hosting, and as their audience grows, they transition to more robust hosting options. I am talking about brochure sites, blogs, directories, portfolio sites, small communities and small e-commerce sites.
All of my potential projects are at a standstill because of this issue. It makes no sense to do a Drupal 6 implementation, if Drupal 7 is not a viable upgrade option because of poor shared hosting performance. I can only assume Drupal 8s performance on shared hosting will be even worse. I am being forced to look at other CMS options. Before Drupal 7, there was no real need to look any place else.