Pretty proud that I beat the game single player. The hardest part was having to do escort missions and missions where you have to carry things. I'd just carry them, drop them, fight and pick them up again. Took forever but it's the best way I found. The last mission and Boss at the end were awesome. Took it back without every getting to play co-op so I have that to look forward to if I pick it up off ebay.
If you skip the side missions the game probably can be beat in 2 days. Beating all missions would take almost a week I'd venture. I was pleasantly surprised and would definitely recommend it as a rental and maybe a purchase if you like RPG's. Some cool Achievements too.