Ranked in these QuestionsQuestion Ranking
Pro Uses LLVM compiler and Obj-C runtime allowing C, Objective-C, Objective-C++ and Swift code to run side by side within a single program
Pro Inherent parallelism
Pro Modern syntax
Pro Works with Apple's Cocoa and Cocoa Touch frameworks
Pro Can be used as a Just-In-Time language
Pro Performance speed comparable to native C
Pro Low memory footprint due to reference counting
Pro Swift has some clever tricks up its sleeve
Due to having elements of a functional programming language. Things like 'map' and 'filter' for example.
Pro Backed by Apple
Con Swift is a moving target
They've released 1.2 so far, and 2.0 is coming soon. Every small update brings adjustments to paradigms (such as how to do type casting) that can be a little frustrating to absorb. Objective C was also constantly updating, however, but not at the same rate these days.