I was looking for a wheeled carry-on w/ backpack straps and chose this one mainly because it has two main compartments.  I used the bottom for shoes and gears and the top for clothes (just like pictured in the product photo) and that was enough for a 2-week trip.  The handles and wheels are sturdy and smooth.  The zippers on the 2 main compartments however are not very smooth and occasionally sticks.

I ended up using the backpack straps once, and only briefly.  It's very cumbersome to get on and off and not comfortable to wear when the suitcase is filled (25-30lb).  The backpack straps also look a little flimsy where they attach to the suitcase, and I'm not sure if they would last very long worn as a backpack.  I looked at some more expensive models of similar wheeled backpacks that comes with a belt strap like a hiking pack, and would recommend getting one of these if you plan on wearing yours as a backpack frequently.

It's not very easy to carry this as a duffel because the handles are on the face (and as some have noted, a little annoying that they don't come apart) and I wish there was a handle on the side (as many carry-ons have) to easily lift.  As others have said, the size of this carry-on is at the maximum of the carry-on limit so don't expand it if you plan on having carry-on only.  Mine barely fits in the United overhead bin unexpanded.

Incidentally, after I got this from Amazon, I found an almost identical wheeled carry-on backpack by Lucas from Ross for $40, and this one has duffel handles that comes apart, though the construction doesn't seem as quality as the more expensive HighSierra.