During a project there is always the data migration challenge. Usually this needs to be quick and fast, becasuse deadline is coming, not too much budget or time etc
Basically you have a few options. One is to use the bulk import feature of MS CRM, but this is very limited in functionality. Other option is to make custom script to import data using the web interface. A third option is go right it to the database (of course unsupported). Finally you could use third party tool.
In my projects we did choose for Scribe Insight software, because it's quick installed and easy to use.
Today I read about the new product of C360 and my first impression is that this will be very interesting option too. The product gives you the ability to import core data in all entities, also custom!, create relationships etc. Very nice is the feature of duplicate checking and data cleansing, because in my experience the data sources are always outdated or full with duplicates.
I will certainly test it on my development system and I think it might be a very interesting option in future projects. More information you could find at C360 - Import Manager.