I get alot of calls from people doing some research on tires prior to buying a new (or used) car, and I can't say it's a bad idea in the least! You'd be surprised how many people damage a tire on their "brand new baby" and are SHOCKED to find out that the fancy 19" wheel and tire option they added now has cost them an extra $50 to $75 more per tire than the stock 18" wheels! (BMW is probably most notorious for this). The OE tires are designed with what the engineers wanted to see from the tire (be it a focus on low rolling resistance, high-speed handling or just an inexpensive tire overall), and may not exactly match up with your priorities (quiet /comfortable ride, long life, etc).
Tire Rack's consumer survey results are an excellent resource to help get an idea as to what others have experienced with most OE tires to help give some insight into what you should expect upon taking delivery and living with the car on a daily basis.
Bottom line? Do a little homework to see if that upgraded wheel and tire package is all that its cracked up to be, or if the run-flat tires the car comes with for "safety" eliminate the possibility of having a spare wheel and tire in the trunk instead. The more questions you can ask before buying the car may lead to less disappointment down the road!