The dictionary defines a refrigerator as "a machine which keeps food cold and so prevents it from going bad." Of course, this definition only works when the temperature is between 33°F to 40°F.
When your fridge is higher -- say, 60°F -- then your food goes BAD. This is what we discovered over Memorial Day weekend, when we had 25 people visiting and I noticed that it just didn't seem very cold in Ye Olde IceBox.
This has taught me two important things about monitoring your existing refrigerator:
1) that you really should keep a thermometer in the refrigerator, in a place that you can't help but look at it
2) that a 'weird smell' in the fridge could in fact be a Freon leak, even though this Freon fact site seems to indicate that Freon never smells. I, however, disagree.
Shopping for a new fridge has also taught us something very important:
ALWAYS Measure every dimension, and be sure to think about how much space the door hinge will need to open properly. We almost didn't measure it carefully, assuming that all fridges were just about the same. NO. The newer refrigerators are HUGE and will not in any way fit into the spaces allocated in older kitchens. Our 15-year old kitchen can not hold ANY of the freezer-on-bottom models that we looked at, and left us with a choice of three side-by-sides to replace our current side-by-side.