The last thing that bugs me, is Pircards whining at the end and Q bailing them out, literally, a Deux ex Machina ending. I get it, that was the point of the episode and Q's actions, to show we are not ready.
But unfortunately, it made Picard seem inadequate, and impotent. If I had been a bridge crew person, and seen that seen, my reaction would have been to lose all respect for Picard as a leader. Maybe it would have been better for Picard to make that admission in the privacy of his ready room, rather than in front of all the bridge crew, whose very lives depend on his leadership?
You see, I had the exact opposite reaction to that scene. I didn't think Picard came off as whiny at all. When you look at Picard's behavior from the last season when he dealt with Q, he really needed a, as Picard said at the end, "a kick in our complacency". As for Picard looking weak to the crew, well, what was the alternative? The Borg were about to assimilate the Enterprise so it asking Q to join Picard in his ready room would have been silly. I think for the crew to see Picard admit to Q's points and ask for help shows that Picard is willing to do whatever it takes to keep his ship safe. Even when he asks for help, he still comes off as strong and competent.
As for Guinan's knowledge of the Borg? Well, you can blame Maurice Hurley for that one. He probably thought giving Guinan a history with the Borg would have been cool, but his execution was significantly lacking. Melinda Snodgrass said in her commentary track for "The Measure of a Man" that Maurice HATES backstories and was quite insistent to keep things in the present.