Omnistar has a fast restart option which has to be enabled in the advanced settings.  If you have convergence, with the fast restart option on you can kill the tractor and come back later, reboot (restart) the tractor/Pro 600 and you will be asked a question:  Has the tractor been moved since it was last stopped?  If the tractor hasn't been moved, you would answer no and the fast restart only takes a minute or two for convergence.  The key is not to move the tractor and make sure it has a clear view of the sky when killed for this to work.  It is a nice feature. 

I typically see 10-15 minutes for initial convergence with Omni XP set at 24 inches for planting.  The biggest problem I have is with dense southern tree lines and moving field to field where obstacles knock convergence out.  I would say that the convergence times are about half as long as they were 3 years ago.  If trees aren't an issue, I think you would be very happy.  I have some fields that require markers to keep me rolling in places, but Omni has improved their ability to temporarily lose signal and get back on track quickly.  You might be able to get a free trial to try it out.