Does burning a DVD/CD slower help assure it will not have errors?

Actually, yes. Faster a disk is burnt, higher is the chance the media may not have recorded it, and consequently higher is the chance of errors, especially with low/cheaper quality media. More detailed explanation here.

The optical media has a lot of error correction.

Burning at fast speeds is said to introduce errors (there is a probability based on environment conditions).

However, most people at CDFreaks seem to suggest that is not really required.

I have usually done writes at full speed (matching the media limits) for data.

For, audio writes, I am a bit skeptical on the theories and slow down a little for safety.

Yet, have not confirmed burning faster would have been a problem yet.

I have a feeling that these audio speed reductions were useful in the earlier days when media, writers and specifically the audio-cd players were not quite up to mark with the optical media handling.

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Specifying slower speeds is useful for correcting errors and buffer underruns. Newer drives with "burn-proof" technology (the opposite of what it's supposed to do; again, who comes up with these names?) are not plagued by buffer underruns as older drives are. [this is in 2003].