I have 3 890 series routers, two fixed bases and two plunge bases. The fixed base routers do have some backlash in the adjustment rack, but it hasn't ever been an issue for me. Once the motor clamp is tight, the thing isn't going anywhere. What I have noticed is that the adjustment knob will move a touch when the router is running due to vibration, and if you undo the clamp it may move a bit. If you put a little tension on the knob before you undo the clamp, this goes away.
I think they're great routers, I love being able to swap out the motors between the bases instead of changing bits, and the motors are great. The spindle lock feature is a little bit of a pain, I prefer to use 2 wrenches.
I rarely use the above the table height adjustment, because out of habit and bad eyesight I still tend to get down on one knee and get a good close look at the bit height in relation to a setup block or scale.
The one thing I think the routers suffer from is they can be a little top heavy when in the plunge base. If you don't set the motor down into the clamp as far as it can go, and chuck up the bit as deep as you're able, they can feel a little 'tippy'. A bigger base plate solves a lot of that.