[EdwardCoffin]

Perhaps this is (at least) a 4th possibility, which is that it would take you time to get used to, but once you had it would not be too much for you. Even Paul Graham (enthusiastic Lisp advocate) once said "I suppose I should learn Lisp, but it seems so foreign" [1]

I found it reasonably readable. The only criticism I had, offhand, was that the predicates like 'is-piece-knight?' were a bit verbose: the query mark at the end is understood to label a predicate, so the 'is-piece-' was redundant. I'd have written 'knight?' instead. That's pretty nit-picky though, and I don't think the current convention really detracts from its readability.

[1] If Lisp is So Great: http://paulgraham.com/iflisp.html