WHAT I MISS IN THIS TOOL
Unable to migrate outlookexpress users, to exchange sadly some organizations have a few (or all) users who have this. Then going into a migration project (outlook&Exchange) i have to say sorry well we cannot migrate your old mail.. altoughh outlook can upgrade this is not always realy usable for example new client PC with pre-installed office.
most i like of exmerge is the advanced logging possible with the tool and also it's more finely configurable then the builtin exhange tools.
In situations when i can not connect to the old server directly by network (be it remote or unstable)
To migrate organizations who don't require PST's beside their exchange mailbox.
I love it that when i migrate to new mailboxes i can reset language of the mailbox.
Also use it with disaster recovery scenario's when retrieveing data from unstable servers instead of move mailbox (not much control inthere) rather use exmerge and keep a watch on the logs it generates