The reason for <> instead of [] is that both are just as ambiguous to Rust's grammar, and that <> is, unfortunately, more-or-less the industry standard (C++, Java, and soon Swift). I would personally prefer something akin to D's generic syntax (but with a different symbol, since the exclamation point already has meaning in Rust).

The reason for using :: instead of . for paths is because the Rust developers did not want to conflate path lookup and field lookup, which would obscure the runtime costs of indirection. (This is also the same reason why you can't omit the parens when calling a method with no arguments: a field lookup and a method call have wildly different runtime costs.)