From a language design point of view, there are certainly some problems with ?:, some of which have been pointed out here. Our approach in Perl 6 has been to try to fix the problems without throwing out the whole idea. One of the problems is simply that it's too hard to see the bits of ?:, so we made the bits bigger. In Perl 6 you use ??!! instead. This also plays into the Perl 6 principle that ? and ! are generally preferred to ask whether things are true or false. There is no natural association between : and the concept of falseness.
Speaking of the ternary operator (whatever it' spelt), I've sometimes felt the need to make it... ehm... quaternary. Specifically, in cases in which I wanted it to return something different on true, false (but defined) and undefined first argument respectively. Now, before pointing out that there are ways around, let me tell you that I know there are tons in Perl 5 and presumably even more so in Perl 6. But I'd also like a syntactically sweet enough solution out of the box, and I wondered whether an optional <c<!!</c> may trigger that:
my $wanted = $cond ?? $true !! $false !! $undefined;