Omega 3 Eggs
In savory dishes that have other strong-tasting ingredients such as onion, no. But I recently made a creme brulee that tasted weird. Then I got the same off flavor in a plain omelette, and I realized it was the high omega-3 eggs. I bought another dozen of a different brand to make sure they weren't just "off" and sure enough, the same taste. I now buy free range eggs from a local poultry farm. They taste great, but occasionally, I get a fertilized one. A bit yucky, but definitely preferable to funky.
Phofiend, if the egg is fertilized and has not been incubated, you really can't tell. If it has been incubated for 24 hours or so, it has a small white donut shape on the yolk--about the size of a lentil, or a little smaller.
Longer than that, and blood veins appear--the yolk begins to look like a bloodshot eyeball.
If you are seeing a bloody spot or small fleshy colored blobs, those have nothing to do with fertilization--they are just signs of slight damage to the hen's reproductive tract.
All of these eggs are perfectly edible, but may be a little esthetically off-putting.