Yes, I have been testing it in a sandbox and it has some peculiarities.
When using the migration tool for SOAP processes, the optional settings in the migrationconfig.xml file has the following two options.
<!-- Set this parameter to 'true' if you want to replace your existing WebService SOAP 3 objects with the converted WebService SOAP 4 objects.. -->
<replaceWS3Objects>false</replaceWS3Objects>
<!-- Name-suffix for creating new WebService SOAP 4 objects in case of replace is 'false'. -->
<nameSuffix>.WS4</nameSuffix>
So based on the above settings, you have two options basically.
Option 1. Set the replaceWS3Objects value to "false". It creates a new copy of the objects for the v4 SOAP objects with a *.WS4 extension and leaves the original v3 SOAP objects alone.
Option 2. Set the replaceWS3Objects value to "true". It "backs up" the original v3 SOAP objects and appends the .WS4 extension onto the backup copies and creates new v4 SOAP objects with the original object name. One additional thing it does without mentioning in the documentation is that it keeps (replaces with backup) the v3 SOAP objects in the workflows, but does not impact usage in scripts.
So no matter which option is selected, it requires manually replacing the usage of the v3 objects in the workflows.
If you want to keep the original names:
option 1. requires backing up and renaming/deleting the v3 objects without replacing them in workflows, then renaming the .WS4 CONN objects and replacing them in the v4 SOAP jobs, then renaming the v4 SOAP jobs to remove the .WS4 suffix so the workflows use the new v4 jobs.
option 2. requires editing each workflow that uses a WebService job and doing a "replace task" to replace the v3 object (which has the .WS4 suffix in the workflow) with the v4 object which has the original name.
My desire would be to have it keep the original name for the new v4 SOAP objects and just start using them in the workflows and just add a suffix for the backup of the old v3 objects since I would be doing this in non-production clients and testing before doing this in production.
So this isn't going to be as simple as it first appeared.