Most of the problems described in this post are related to the hosting plan used by these users or due to another circumstances that are not related to Sitefinity itself. If you have some doubts use VPS or dedicated server. Shared hosting plans are not suitable for big websites and websites that expects big traffic.
the Telerik team
Do you want to have your say when we set our development plans?
Do you want to know when a feature you care about is added or when a bug fixed?
Telerik Public Issue Tracking
system and vote to affect the priority of the items.