Thanks for the reply. Performance and ease of use are two of the criteria we're attempting to evaluate so your experience is very timely.
We're engaged in a consolidation project for several clients and are considering using mount points to increase the number of instances being hosted on a server/cluster (to mitigate the problem of not having enough drive letters for the physical volumes involved) and, where the customer wants to host databases for multiple applications onto one instance, isolate storage usage so that any one set of application databases does not cause problems for other application databases when unexpected storage usage event (e.g. from an INSERT/UPDATE/DELETE query using up all of the transaction log space) occurs. Using mount points would also give us the flexibility to add space easily.