I have had good experiences with the Clariion CX(400, 500, and 600) line but would stay away from ATA drives for VMware. They are very slow compared to FC drives and have a much higher failure rate when used heavily.
I am also pleased with Dell. I assume you are looking at a pair of 6850s. Neither IBM nor HP come close to the price, especially when bundled with ESX.
I can't comment on connecting multiple hosts to an AX100(should be possible) but a single server can certainly access two arrays.
We're somewhat in the same situation. Currently we were looking for the Storagetek FLX640 with SATA disks but it doesn't seem to be supported by ESX. We already have a FLX280 for ESX but this particular SATA SAN would be used for only one VM for backups so IO isn't necessarily as critical as if it was shared with multiple VMs (like the FLX280 is).
Any suggestions ?