I haven't owned a 690, but I have owned a 660 Rally 2006. And Rally Replicas are really nice pieces of kits. They are really exclusive and very well engineered bikes that will last a lifetime. But some bits are extremely expensive so if you strike some bad luck you will have to take out a mortgage on your house whilst crying over the KTM invoice. But like I said, the bits are engineered to last, thus the hefty price tags. It's sort of a shame to use it as a daily commute but on the other hand, the smile on your face will be big when arriving for work.
Only you can decide whether or not the bike is worth it. It is a RACEbike and not a tourer and will of course require a lot more looking after than a standard 690.
Hope it helped.
(I'd never use one as a commuter!