Hope this discussion isn't too old, but we have a similar question. We plan on using slow SATA storage from our netapp SAN as the shared storage but with FusionIO iocache cards on each esx host to provide much higher IO performance on the reads (90/10 for us). FusionIO is much faster than SSD so we're not sure if we should put ssd disk in each host for the swap files so that they're not writing to local disk that's slow for the swapping. We'll have plenty of memory but some applications/os still use the swap file regardless.
Will the use of FusionIO and no memory constraints deflect any benefit of ssd on the host? (poweredge r720).