The degree of extra difficulty in UEL once you're used to it is really very small. Sure, the lies may make your approaches a little more difficult to judge (particularly downhill shots); your tap-in birdies might turn into 4 or 5-footers and your 10-footers into 15. It forces you to play for fairways and greens a little more instead of being in all-out attack mode on every shot, and it tests your mid-length putting more than usual. Any mistakes are magnified, but good players don't make many mistakes.
If you do miss the green, you can actually use the slopes to your advantage like the pros. I was in the bunker short at #11 Oakmont in the weekly tournament, facing a front pin, and expected to have an 8-10 footer for par. But I had a steep (yellow) uphill lie in the sand. I doubled my normal shot distance calculation and it popped out super high and trickled down to tap-in distance.