Less Challenging
Elasticity: Elasticity is a hallmark of Software-as-a-Service, just as with IaaS and PaaS. However, while capacity may be elastic for most SaaS solutions, the pay-per-use model may not be. Some publishers will make you pay for X, and you don’t get to scale back on X if usage drops. It all depends on the agreement between your organization and the provider.
Management: SaaS offloads a significant amount of traditional work from internal resources to provider resources—even more so than hybrid clouds. This resource savings potentially can be reapplied to focus your IT organization on strategic business needs.
Mobility: Most Software-as-a-Service providers offer mobile application integration as part of their overall offering. The ability to deliver a mobile application experience has proven to be a high value accelerant for moving applications to SaaS providers.
Somewhat Challenging
Control: Some publishers give you total control over their software, while others are highly restrictive. SaaS is no different, but with the added element that delivery of the application is handled by the publisher.
Security: SaaS has a neutral security posture when compared with security and regulatory concerns a customer may have with IaaS and PaaS. With potentially sensitive information passing through the hands of a third party, and with the highly fluid nature of multi-tenant environments, it can be difficult to know exactly where and how well secured your data is at all times. It may also be challenging for your organization to verify information security compliance.
Resilience: Most SaaS providers today offer highly advanced redundancy with uptime guarantees. Many variations of service resilience are available, so a thorough inspection will be necessary before committing to a financial agreement.
More Challenging
Flexibility: SaaS offers some flexibility, but only within the parameters established by the publisher.