I too have found it difficult to take the step after all it's quite an investment on many levels and I have been using VW for a long long time and don't want to give it up. The decision by NVW to drop Machine Design and therefore not develop that side of things further started me considering my options, and with recent frustrations in 2011 I have to taken the plunge. Especially as in the Machine Design world VW is quite far behind.
In answer to your question, 'how difficult the transition had been', it has been easier than I thought, although I am still using VW and it's still early days, but learning the basics and producing drawings has not been difficult. The tutorials are helpful and utube has a fair amount of videos to help as well.
Filleting, chamfering, 3D dimensions, EAP's etc all seem really good and the lofting even carries a history.
OpenGL works very well and I have had no crashes or freezes...yet!!
So far a good experience