I haven't had much time for resolutions of the Synoptic Problems along the "have your cake and eat it" lines of Matthew knew Mark, Luke and Q or Luke knew Mark, Matthew and Q, but a note at Euangelion, "A Defense of the Holtzmann-Gundry Hypothesis on the Synoptic Problem," (siding with the latter solution) does give me pause for thought.
After all, most times cake is offered to us, we get to eat it too, so why not in gospel scholarship? There are bits of Luke which are explained by his knowledge of Mark, bits that are explained by use of exactly the same non-Markan source as Matthew used, i.e. Q, and bits that are explained by use of Matthew.
Yet problems remain. Maybe most pertinent in my thinking is Luke's Parable of the Pounds versus Matthew's Parable of the Talents. If Luke knows Matthew, why doesn't he use Talents? It is well written and has no awkward bits like Pounds has?
Of course one could posit a staged process of composition. Luke gets to see Matthew after he has composed bits and bobs of his gospel and, in the Talents/Pounds case, sticks to his own story "warts and all."