I chose to buy BioOpen after struggling for years with various open source and home grown programs. I was attracted to the idea of harnessing the often excellent open source programs that are out there into a single app with capacity to hold together a bunch of sequences relating to a particular project. It was obviously new software and I anticipated the odd glitch. After 6 months use I'm very happy with its performance, and with the rapid response of the developers to the few problems I've found (all to do with interface rather than data integrity).
I use BioOpen principally for planning construction of expression plasmids, so most use the restriction enzyme, ORF and alignment capabilities. All are good. The 3D imaging capability is nice for correlating structure with sequence and for fairly quickly obtaining nice pictures, but I still use VMD for anything heavier. It handles lots of formats and eases interaction with the many web-based services I use.
The principal competition is MacVector which is more comprehensive, more mature, and much more expensive. The interface is old, copy protection irritatingly pervasive, and in my experience (prolonged problems with local proxy servers), their commitment to technical support is weak. Much of what I do is done well by GeneConstructor. but that feels very much like an Os9 app just managing in Os X, and has not been updated for years.