EcoFastPacks

I had never used these before, but then again, I hadn't moved in over 15 years so the idea of renting boxes sounded interesting.  
In fact, it was great!
The boxes are heavy duty plastic with lids-- and zip ties and tags are also provided by EcoFastPacks.
Basically, you order the delivery of the boxes (they also give you a special dolly designed for the boxes).  They bring them to your location... you fill them... you move... and when you empty them, they come and pick them up.
No buying boxes, and tape.  No assembly of paper boxes.  No breaking down the paper boxes. And no trash waste from the paper boxes.
You can stack them up to 5 boxes high... and with the dolly they provide, one person can move them!  (I did, and was amazed at how convenient is was!)
The only two downsides are:
1.  The boxes are a little heavier than paper boxes
2.  You have to unpack quickly in order to avoid additional fees for the weekly rental.  (Which is also an upside because it makes you unpack right away)
It was even cheaper than buying boxes in the end, for me.
And although I mentioned the two downsides, I have to tell you, I had the boxes for much longer than I'd rented them for-- and the owner of the company didn't even charge me... but you do want to take into consideration for how long it will take you to unpack the boxes when you rent them.
All in all, they boxes were an excellent choice.  I hired movers and they used the boxes as I'd asked.  They were used to the paper ones... and they were the ones who said the boxes were a little heavier, but I think the fact that the boxes hold so much makes one want to put more in them-- which makes them heavier.  But if you use the special dollies (and don't have a lot of stairs like I did), it's a life-saver when you're doing it on your own.  And even with the stairs, I found I was able to get more moved on my own because of using these boxes.
I highly recommend!