I only tried using an actual "seed starting mix" (or whatever it was actually called) one time, and can't remember now what brand it was, but I had the worst germination ever that year. I just use regular Miracle Grow potting soil for almost everything; I'm sure it's not the best thing but it seems to work well for me. And I've started using vermiculite for very tiny or notoriously difficult seeds, which has also worked well for me -- I got great germination with rosemary seeds this year with the vermiculite; in the past I've had a hard time getting them to grow at all.
Although I do get the potting mix pretty wet when first starting the seeds, I tend more to underwater than overwater after that... but I agree that overwatering is by and large a more common problem for seedlings.