Yep, I used it for both labours and found it really helpful

There's been a few threads I think, maybe do a search for more info but
With Jasper - I laboured at home for 3 days before going to the hospital (checked in at 4cms). I had the TENS machine on constantly while I was at home, and I found it great to distract myself with the buzz. I didn't feel any 'pain' after he turned the right way (was posterior to start with) - but I don't know whether that's the TENS or just the way I labour. I took it off just before I had my shower at the hospital and the epidural.
With Jovie - labour was much quicker this time, so I didn't spend a long time on it, but it was the only pain relief I had this time. (I put it on after my waters broke, checked into hospital at 8cms, she was born about 45 mins later - so all up maybe 2.5 hours of it). I specifically remember holding onto DH's hand with my right hand, TENS machine in my left hand while transitioning, LOL. It did help me again to distract and focus on the buzz sensation - when I pressed for it to amp up, I'd used it as a reminder to breathe slow and deep, which helped me alot. I also kept it on while birthing the placenta, just in case I needed it (didn't really).
I highly recommend it

I hired mine from mamatens.com.au - they sent it out when I was 37 weeks
I really liked the idea of being able to get up and walk if I needed to, or you could lie down into it, it can clip onto you with the belt provided, or you can hold it in your hand.
There's levels of buzzing (for lack of the right term) - I never got past step 2 (or A2, whatever it is), didn't need it to go any higher/stronger but it was good to know that it did go higher!
Remember to put it on as soon as you feel the first contraction
let me know if you want any other info on it