I'm not claiming to be an expert on Lithium batteries, but I do know there are a couple of things to be cautious about. First (and the service manager's primary concern) was that they operate at slightly different voltages than sealed lead acid. A fully charged SLA battery will typically be around 12.8V. A Lithium battery will be >13. He said the multiple processors in our bikes got temperamental with the different voltage. Secondly, Lithium batteries charge at a different voltage than SLA and you'd want to make sure that the charging system on the bike would sufficiently charge it. Third, many people put their bikes on a "float" battery tender while it's not being used. Lithium batteries do not like this and can be damaged by leaving them on an extended float charger.
If anybody has any specific knowledge and can speak to any of these issues, I'd appreciate the education.