Most definitely.
I'm well aware of its shortcomings, but if you're not using it, I feel like you really only have a fraction of the iPhone everyone else has.
To me, not using Siri is kind of silly when I think of how long it would take to: unlock the phone, open phone app, select contacts, select the letter on the right and then scroll through to find the right name, selecting the name, selecting he call button, versus just... "Call mom."
I use it while I'm running to open apps, play podcasts/music, and to read and respond to texts. I use it to get directions somewhere way quicker than you can by any other method. I set super-quick timers when cooking or doing laundry. I check sports scores way more frequently and quicker than you can otherwise. Anytime a thought occurs to me, I keep from losing it by quickly creating a new note, adding it to my to do list, shopping list, reminders, etc., my calendar, or even recording a voice memo.
And as dissatisfied as I still am with Siri's limitations, it is dwarfed by how dissatisfied I am with Apple's touch keyboard experience on this tiny screen. I can write down everything from a quick text to long paragraphs about a project or idea I'm working on so much quicker and with better accuracy. It's really hard to imagine writing anything longer than 100 characters or so without it.
I'm hoping that with iOS 8 and extensions, that it continues to improve.