I'm wondering if you have any benchmarks or performance considerations with regards to Mapping Data to/from DTO objects? Are there auto-mappers that perform tangibly better at this? How does ServiceStack's built-in mapping feature compare with competitors? would several mappings back-and forth create a noticeable performance degradation in an application?
ServiceStack built-in AutoMapping is pretty fast/tight where like most of ServiceStack uses cached delegates to avoid runtime reflection. It outperformed AutoMapper when I tested this years ago, but as always I recommend doing your own measurements/benchmarks. It's unlikely Auto Mapping is your bottleneck.