The problem is that a device will send an ARP request and it will bind only one MAC address to the IP address so only one host will be used, or the ARP entry will change according to who sends a packet thereby destroying session integrity. It's not a switch issue, rather an IP stack issue.
If you want to load balance in any sensible fashion, a Content switch such as the 11xxx range will be a better solution. If you need any assistance contact stevep@cisco.com and I will assist.
