Easy enough to recover from that, just double tap the word and choose "replace", then tap the original word.

I do have the problem that I suffer from occasional brain fade and tap the replacement to dismiss it when in fact the replacement was exactly what I meant to type. I also realise that I am about to do it a fraction of a second before doing, but not in time to deflect my finger from its target...

All in all I think the iOS correction system worlds well, even with its little quirks.