My company uses Zendesk Sell (formerly Base). My business partner loves it and uses it religiously. I haven't used it quite as much but I really like the UI and

My company uses Zendesk Sell (formerly Base). My business partner loves it and uses it religiously. I haven't used it quite as much but I really like the UI and I've done a few API integrations with our internal systems. The mobile app is also really impressive, at least from a technical point of view. Salesforce is a very different kind of product however, I don't think ZS offers anywhere near the level of customisation, or at least it doesn't at the level we pay for. For a small business like ours ZS is perfect.