My saw table came with the router fittings as part of it, and I have found it to be quite workable for the things that I have done. When I set the height of the router bit, I do use the stops nearly all the time. This allows me to drop the router when I am not using it, and then put it back up at the same height if necessary. As has been commented in other posts, space is at a premium, and if I didn't do this, I wouldn't have a router table at all. The biggest pain I have with my saw table is in fact the guard and riving knife. They are all one unit and I am frequently removing them just to set the angle of the saw etc.
Although I can move the saw fence to where the router is, I don't use it for the router. Instead I have a piece of 70 x 50 that runs the full width of the table that I clamp to the table where needed. (50 x 70 = 2" x 2 3/4" approx) I cut a channel out of the 70 x 50 in the middle so that I can put it over the top of the router bit, which is something you can't do with the saw fence. This channel also gives somewhere for the sawdust to go when it comes out of the router and keeps the job a bit cleaner.
I don't find height an issue, but I have raised the saw table by putting 2 bricks under each leg. It's hard to explain simply, but I needed it this high to get longer lengths of timber over other obstacles, and with 3100 (12') ceilings, I end up with quite a few longer lengths. Just to complete the picture, my scroll saw sits on the table saw over the top of the router because I don't have any other space. This means I have to drop the router to use the scroll saw, or put the scroll saw on the floor to use the router. Given that, you'll probably understand why I haven't gone for a separate router table - there just isn't the space.
My 2 biggest issues with the router in this setup is changing the cutter and setting the height for a job. There really isn't enough room to change bits easily, but I've found the best is to lift the router up as high as possible and remove the cover place over the router hole. I have a plunge router, so setting the height is a matter of pushing up against the spring. I use the stops in a trial and error mode to find the right height, and once the height is set correctly, I don't touch the stops unless I have to.
The cast iron table is quite solid and I don't have any issues with vibration etc.
That's my experience.