My 07 400 has 55k+ miles on it, and yes, my steering bearings are notched. I Can EASILY feel them. Been that way for 2 years now, last year the guy that does my VA Inspection (whom I trust, which is rare for a mechanic) warned me that it might not pass next time around, he did warn me 2 years ago, and noticed last year that they were worse than the first time around. Well, I'll find out next month when its time for re-inspection in august if it will pass or not
For me personally, it does not effect how it rides or handles, i mainly only notice it when turning the handle bars at a stop, or at "walking-the-bike" speeds, never really notice it while moving.
Going off memory of when I looked into it a year or so ago, its 2 bearings, and they were about $30 a piece at a local bearing shop (not OEM, since its just a standard tapered bearing), but the labor to change them was a lot of work, lots of tupperware to remove, and a lot of cables and wiring.
My daily commute involves alot of city traffic, on poorly paved streets. However, after the many many years I've drivin on this junk roadway, they JUST finally paved the worst section of it last week, its like heaven now, but still a few 'speed bumps' if you will in the middle of the roads. These are what notches the bearings over time. Hard hitting bumps, and usually done when steering is straight, so it hits on the same spot over and over again.
As far as me riding with the bearings the way they are, that is my personal choice. In my personal view, its safe, while to others, their views might differ. With the 'notching', I don't feel the steering is hampered, nor do i feel that the steering is going to lock up in the middle of riding. But please do not take my views as how you should proceed in your situation.