The problem with Apple is that updates are usually pushed out yearly (with each iOS introduction). With Siri the only new developments/exceptions that have been announced are new language compatibility and minor capability improvements (reservations, ticket buying...).

Now, ¿Does that mean that Siri hasn't evolved at all? Not necessarily. Server-side it might have become more reliable or accurate without Apple promoting it, for example.

Personally I use Siri as a shortcut for some functions that otherwise will require to many taps or navigation. Every day I set up my next day alarm with it "Wake me up at..." and sometimes I set up appointments using it. I might ask her to read me some message if I'm running, too. Some of those things Google Now / Android does not offer in it's current state.

I've never had any reliability problems so for me the service has not improved. Maybe users with thicker accents or that had trouble at the beginning would be able to tell otherwise. This has been the case, for me, with iOS Maps. Not new big banner features since introduction but constant improvements without publicity.

On a side note, another two cents: Siri's buzz didn't have to do with the product itself but with the glimpses of the future it offered. It carried the message that sooner or later our way of interacting with things will be a mix of gestures and voice.

It faced the same problems other speech recognition systems and virtual agents had in the past (including pre-Apple Siri) but the fact that a company that caters to the mass market was ready to give it a push probably caused a significant shift and raised awareness to this technology. Certainly has become a well known feature even by common, non-techie users. My mom or my grandmother knows about it, even if they don't use it. That is a huge step forward, in my opinion. Theres always time to refine and improve.