A Non-Sales Viewpoint:
ZIllow has a great culture and is full of amazing and intelligent people. If you want to work in a tech job with great work/life balance, amazing benefits, while surrounded by smart people, you should work at Zillow.
Hardest Part: The technical challenges. I think this should be the hardest part, because you aren't learning anything otherwise.
Most Enjoyable: Free lunches, co-workers, solving challenging problems.
ps- The CEO is awesome, everyone loves him!!
401k match, free lunch, game rooms, standing desks, candy wall