It just looks better with them

Can't agree with that, but taste is a personal matter.

IMnsHO omiting the parents is just as clever as omiting the curlies in if statements in C or JavaScript. Something you can do, but sooner or even sooner it'll bite you.

I can easily see the failure mode with omitting curlies in C or JS, but I don't see what could go wrong with ommiting the parens around the if condition. Care to elaborate?

The only thing that might become confusing is when you use a map or grep with a block without additional parens. But that's only a rather rare case, and IMansHO not good reason to include visual noise in the general case.

(I might also add that I've written a fair bit of Perl 6 code already and haven't been bitten by that)