What do you like best?
Very flexible tool with possibilities to be discovered as you grow into into using its full potential. One of the best (basic) features: you design one survey (questionnaire, ballot, poll, report form...) and can use it - in different designs - as online or offline (paper) tool.
The design and extent of real time results (publishable online) appear to be endless. Beautiful graphics make results easily understood.
Once you know your way round Sphinx you can even construct an individual score for one person (e.g. a personality profile) as well as a summative report for the whole sample, using various statistical procedures. At least in Germany (may not be true for all countries) the support is superb, friendly, helpful, highly committed - to your interests, that is.
What do you dislike?
The statistical procedures available are somewhat odd and limited. If Sphinx would improve here, a lot could be gained. However, it is possible to export data (e.g. to Excel, SPSS, csv ...). Tools for qualitative analysis of data are available as add-on, but somewhat rudimentary.
Recommendations to others considering the product
It is a "big", but scalable solution. Depending on usage you may want to use their online services (can be fairly expensive in the long run). With regular usage your own Sphinx server may well be worth the cost.
What business problems are you solving with the product? What benefits have you realized?
Ongoing evaluation of workshop trainers by participants of the workshop, results published in real time, individual scores available to each trainer.
Various research projects have been supported by Sphinx. The largest project to date had more than 9,000 participants.