We integrated with pendon for our SaaS offering so we could build out an onboarding process within Salesforce's Chatter feature (which was great!). I think it took me 2 weeks of learning how things worked before my team felt comfortable adding functionality or building custom components/apps themselves - this isn't something anyone should expect! That said once built though there aren’t many limitations beyond what might typically be expected when developing internal tools / apps as part of another larger application stack such has SFDC + Slack etc.. There were very few issues around integration but one time did take longer than normal due possibly because their API changed unexpectedly at midnight while integrating into ours during peak usage times :). Definitely look elsewhere if more customization needs must then consider writing integrations yourself rather then relying solely upon 3rd party services. Building self service user flows & automating some manual processes related directly back to sales reps'.