I've sparred against a jujitsu guy and had a problem when he dropped down low and gave alot of body punches - complimenting this by bobbing side to side and popping back up every now and then to do hooks. To be fair we were both wearing boxing gloves (which is a little disadvantageous to wing chun), but it's definately good to pressure test against different styles to see what works and what doesn't, as well as trying to make the basic WC principles work for you in a much more realistic setting. His main comment was that my head (and body in a face-on stance) was always in the same position (as opposed to constantly bobbing and weaving like his) and he always had a fair idea where it would be at any given time.
Another thing that made it difficult to deal with him dropping so low is that I'm a relatively short guy, so am not used to dealing with an opponent smaller or lower than myself. It's all good though as if you don't experience such diversity, then you can't grow.
In the worlds before Monkey, primal chaos reigned. Heavens sought order. But the phoenix can fly only when its feathers are grown. The four worlds formed again and yet again, as endless aeons wheeled and passed. Time and the pure essence of Heaven, the moisture of the Earth, the powers of the Sun and the Moon all worked upon a certain rock, old as creation. And it became magically fertile. That first egg was named "Thought". Tathagata Buddha, the Father Buddha, said, "With our thoughts, we make the World". Elemental forces caused the egg to hatch. From it came a stone monkey.
The nature of Monkey was irrepressible!