VMware have released Converter 5 which has some really handy new features the two big ones being vSphere 5 supports automatic partition alignment (which is huge in a shared storage environment) and SSL traffic for conversions.
I have noticed it can be a much slower than 4.3 which can be due to the the following reasons:
1.Reducing the partition size will change the file copy method and switch from block based (1′s and 0′s) to file based (think fragmentation / seek speed / etc), which can really slow things down.
If you are increasing partition sizes, this does not apply.
Recommended practice would be to just drop the allocation method to Thin provisioning (which you can do right from inside converter)
2.If you are running Converter 5 with the default settings, converter is encrypting all traffic from the source machine to the ESX(i) host over SSL. On older machines (or machines with a tight maintenance window), this is especially painful. Either way, if you want the fastest possible converter experience (and don’t care about someone sniffing your conversion), Disable NFC SSL in the converter configuration file (steps taken from the converter release notes):
Disable NFC SSL 1.Open the converter-worker.xml configuration file. It is usually located in C:\ProgramData\VMware\VMware vCenter Converter Standalone folder.
Set the key Config/nfc/useSsl to false. Save the configuration file.
Restart the VMware vCenter Converter Standalone Worker service
3.Another issue I have come across is UAC. If this is enabled then it could also cause issues with connecting to the remote server. I would advise now making sure UAC is disabled on the source and remote machines.
I will keep updating this blog post with anything else that I find in relation to VMware Converter 5.