VMware converter is also doing V2V conversion. As you said that copying of vmdk is taking too long hours might it is possible that the VM is power on either you could down the VM and copy the vmdk or do V2V
There are other ways to do also.
1. Take a backup using VCB http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1002978 and restore the VM using vmware converter to your new esxi box
2. If you have a vCenter server if not you can download the evaluation version of vCenter Server 5.0 and add both hosts 4.0 anbd 5.0 in vCenter Server. Create vmkernel port and power off the VM and migrate the VM.
