Over the past 5 years we have adopted synergy as a standard tool across the company. Uptake was initially slow however now it is now accepted as a highly capabale robust tool. We currently use over 300 licenses across the company and we are looking at expanding it.
The featues and UI which have been introduced in the latest versions address many of the issues which users complained about when we first started.
Synergy's future direction of using coporate sign on is a step in the right direction however they need to address some key issues before this aspect of it can be used in anger. (This should be fixed in the next release hopefully)
Like with all complex products training is a key aspect to getting the most out of it. Synergy works in a different way to which people working with other tools in this area think and it can be a challenge to get people to change their thinking. However once they do it is well worth it.
Combined with the tight integration with Rational Change, Synergy gives you 99% of what you need out of the box to do the simlest development to the most complex development.
We would recommend Synergy for any organisatino which is serious about configuration management.