Personally, I'm not a terribly large fan of the cross-class skill idea anyway. When skills are pretty much defined for you as "you can take this skill" and "you probably shouldn't bother taking this skill because you'll never be any good at it no matter how hard you try", that pretty much caters to stereotyping. Everyone knows, for instance, that fighters are blind as a bat and couldn't pass a spot roll to save their lives.
In 2E, at least, purchasing a proficiency across class lines may cost you extra, but you'll still be able to be good at it. In 3E, not only does it cost you extra, but you'll always suck at it no matter how hard you try. It's rather restrictive in that way: You can't REALLY develop a character which is somehow "different", even if you wanted to: A fighter, for instance, could never really be someone with a passionate interest in security, particularly traps: Even if you tried really hard, and had a good int, all of those skills are cross-class: No matter how many points you'd want drop into it, you run into a hard cap of half that of anyone else. Rogue skills are similar: In 2E, you could really begin to develop a field of specialty by 3rd level. In 3E, the limit of how many points you can even put into a skill at all effectively forces you to spread them out, and as a result, many of the skills are mostly useless until higher level.