What sales compensation tools have you used/using and what have you learned that would have changed your decision (if given a do-over)?

@Candi Bashiri - I've used both CapitvateIQ & Spiff (currently on Spiff). They have similar functionality but I find the UI better on Spiff. Of course CIQ may have made improvements. We switched tools almost 2 years ago. Salesforce just purchased Spiff so I assume Salesforce and Spiff will be more tightly integrated going forward. For both tools I recommend to keep reporting in mind when building out formulas and structure of compensation plans so you do need to do re-work to improve reporting later.