I use Siri just about everyday. I find it very useful. I don’t remember the last time I got an “I’m having trouble right now” response. The misunderstandings are infrequent enough to be funny rather than annoying.
The frequent recognition problem that does happen enough to annoy me is, “Set an alarm...” For some reason Siri has a hard time understanding me when I use that stock phrase.
My biggest complaint is that too often it seems to think I’ve stopped talking when I’m in the middle of a word. In general, though, I’m not a big fan of that feature with either Siri or voice dictation. If it worked better, it would be OK when using Siri most of the time. When doing voice dictation—and when doing voice dictation as part of a Siri interaction—my speech often needs to pause to wait on my mind.
Oh, and there is one other minor annoyance with Siri. If I say something like, “What is the closest Chinese restaurant?” Siri shows me a list of the closest ones. Once I tap on one of those, it takes me to the map. As far as I can tell, there’s no way to get back to Siri’s list short of asking the question again.