For mine, I didn't think the shimming was any problem- I only used two washers for each side. The swaybar was a bigger problem for me- I used a WRX swaybar, which mounts differently on the control arms than the older ones do. I had to do a lot of hammering and wrenching to make everything work. The old bar might have worked, but I had already gotten rid of it. I think some subframe mounts have to be grinded to make everthing fit, too.
But anyway, back to the shimming... I regularly autoX and have rallyX'd the car, and there are no problems so far.