My husband and I put this together over two afternoons - My guess would be about 6 hours.  It may have been less if we hadn't been battling very cold, windy conditions.  Seems to be fairly sturdy, though the metal is on the thin side and it did arrive with several dents which was disappointing.  We're going to be using it as a temporary sheep barn and then later for hay storage, so it's not a huge concern for us.
The assembly was certainly tedious (lots of fumbling around with over a hundred small screws and washers), but doable for the two of us - I'd describe our DIY abilities as intermediate.  The video on the product page was helpful for steps that weren't super clear in the printed instructions.
For the price paid, I'm satisfied with the purchase.