Of course, we still need swap for COS, but it is swap partition I also always set to 544MB. But on ESX2.5.x I must set also vmfs partition on esx local storage for swap file for VMs. This in esx3 looks like not needa couse swap file is located together with vmx, vmdk etc of conrete VM. So question is if it has any usefull reason to make vmfs partition on local storage where ESX3 is installed or is better to make any other partition bigger (which one?).
That is correct. The swap file used by 2.5.x is no longer needed since 3.0 stores the VM swap file on the VMFS with the VMs configuration files.
So, you don't need any additional swap partition to take over for that. Now, if you wanted some additional VMFS volumes you might consider placing one on your local storage if you have the space and you can envision a use for it in your environment.