I am no scholar of the synoptic problem, but I was raised a Q sceptic and continue to remain comfortable with the notion of Luke's knowledge and use of Matthew.
But I looked again at one tiny aspect of the evidence that Mark Goodacre draws on in support of that notion: namely that Luke betrays apparent knowledge of the Matthean Birth Narrative at the following point:
Luke 1:31: καὶ τέξῃ υἱὸν καὶ καλέσεις τὸ ὄνομα αὐτοῦ Ἰησοῦν.
Matthew 1:21: τέξεται δὲ υἱόν, καὶ καλέσεις τὸ ὄνομα αὐτοῦ Ἰησοῦν·
See, The Case Against Q, 56–57.
So far, so good. What is puzzling, however, is that Matthew continues as follows:
αὐτὸς γὰρ σώσει τὸν λαὸν αὐτοῦ ἀπὸ τῶν ἁμαρτιῶν αὐτῶν. / and he will save his people from their sins.
The issue is that on the face of it, at least, this further clause would seem eminently in keeping with Luke's redactional interests. While Luke's use of the verb 'to save' is broadly similar to Matthew and Luke, the language of 'salvation' and 'Saviour' is distinctive not least in the following canticles (see Luke 1:47, 69, 77). It might, of course, be suggested that Luke has no interests in Matthew's etymological comment, or that Luke replaces the Matthean clause with the more explicitly Davidic: οὗτος ἔσται μέγας καὶ υἱὸς ὑψίστου κληθήσεται (Luke 1:32). It is also true that the notion of deliverance from 'sin' is always expressed using the verb aphiemi in Luke, rather than sozein. Nevertheless, the Matthean formulation would appear to be conducive to Luke's overall concerns.
I don't have access to Michael Goulder's Luke: A New Paradigm (the library copy is out), so it may well be that he offers an explanation there.
Any thoughts, Mark?