A successful mobile deployment using ActiveSync depends on giving users a reliable, stable sync experience. But if any of the many moving parts in the EAS data path fail or degrade, the experience will suffer.
This commercial open source CRM solution (available in a free community edition or in various supported configurations starting at $40 per month) doesn't have an iPhone-specific user interface. However, we think SugarCRM is sweet for two reasons. First, the basic application is easy to deploy, customize, and use. Second, there's no need to deploy a separate mobile application. Just access the server from your iPhone's Safari browser with the standard URL; the application detects that you're logging in from a mobile device and reacts appropriately.