The pro model is for people who want an os, but with little more added to them. The hard coated crank and ceramic bearings make this motor an interesting option, but would I buy it? Probably not, since I would also prefer a JX instead or spend a little more to get a Speed II from OS, but it is an option since the JX does not come with a ceramic bearing. For the 400, I'd also try to find the older speed with the aluminum head for the same amount. I've bought 2 speeds for that price. For less then 400, the toro is a good motor to look at, but I still think the motor has to suit the driver more than anything.
As far as other motors available I would give a toro a good look, heck even the Plus 4 for most people is enough. I just like the idea that OS offers an inbetween motor in their lineup. Is the price right for the pro model? It might be a bit high, but that's up to the user to determine what they want and need. I would think the price would come down a little, but I would not get it since I already run speeds and novarossi's.
To me, if I'm gonna start investing in new motors, then I would give the JP eagle series a look. These motors are selling on line modified for around mid 400's where I've seen them. A local racer at our track has one it looks outrageous on the track.