Having installed many IKEA kitchens up to this point I feel there are many advantages.
1) As cost is a primary concern for rental properties, they can be very inexpensive to purchase and assemble.
2) The overall look can be made to look higher end with simple tricks such as crown molding along the upper cabinets, bull nose and undercabinet lighting.
3) To further the appearance, inexpensive mosaic tile back splashes can go a long way.
4) Let`s not forget that it is still a box with a door. Particle board for the carcass is perfectly fine. I have seen many kitchens in high end homes use a particle board base carcass. The trick is using wood veneered pieces on the ends to give the appearance of a solid wood.
5) Hardware can go a long way to giving a higher end appearance.
6) There is usually a sale on once a year where you can get a %10 discount on the total kitchen. They give you credit in the form of gift cards which can be used for anything in store. ie appliances, decor
I would beg to argue that the average person could not determine the difference between a well installed IKEA kitchen and one from one of your local installers. The 43mm system that IKEA has been using for over 20 years has remained largely unchanged and has been copied by many cabinet makers today.