Apple made a big deal about Swift eliminating certain programming errors, but coming from the C/C++ and Java worlds, it didn't eliminate the two of the biggest headaches for me.
First, variable type declarations are optional with the variable taking on the type of the first value assigned to it. While this is better than C since it eliminates the void type, it still can introduce some pretty big headaches if you're not careful. I can already imagine spending quite a bit of time trying to track down a bug where a variable ends up getting initialized as an integer when the code's original author thought it would always be a float. That's why any Swift code I write will always declare the variable type when I create the variable instead of waiting for initialization.
Second, Apple just created a nasty stew of legacy issues. I worked on a product that went back over 10 years, and it was a confusing mix of both C and C++ code. The two were mixed together in strange ways, and it made maintaining that code quite confusing. Apple has created a situation where C, Objective C, and Swift code can all be in the same project. That's going to create code maintenance issues.
Finally, so many of the features that I've read about just feel like Apple is playing catch-up. I'm not very familiar with Objective C, but the fact that Apple is plugging generics, maps, and advanced lists has me scratching my head. Where those things missing from Objective C? If so, just.... wow. Java has supported generics since 1.5 was released 10 years ago, and advanced lists and maps since 1.2 (released Dec. 1998).
To be fair, I've only skimmed Apple's Swift Programming Guide, but I saw very little to get me excited. Swift does not seem to break new ground in any way. At best it brings in some design patterns which were sorely lacking and finally brings Apple's language du jour into the 21st century. Given the fact that Apple's peers, such as Microsoft and Sun/Oracle have been giving their developers these tools for quite some time now, Apple's development of Swift doesn't seem all that praise worthy to me. Seems more like they deserve a slow golf clap for being the last runner to cross the finish line.
Edit to add: Don't get me wrong here though. There are things to be excited about. But it seems to me all the cool wiz-bang stuff we saw were features of XCode, not Swift. XCode has always offered many features that other IDEs lack. But there's a difference between an IDE and a programming language.
