1) Do you think that anyone gets "lost" in the Weasley family? It's a big group with a lot of strong personalities there. Does everyone get a fair look in?

Ron when he was younger, perhaps, and I think actually Percy among the siblings, at the very least, which may have had something to do with his distance from his family later on.
2) How do you think that Molly and Arthur's relationship has impacted on their brood and how they see the world.
Molly and Arthur's relationship and general personalities both greatly effect the Weasley brood- they see love, family, friendship as probably the most important things in the world, and many of their most basic views come from their parents. Mr and Mrs Weasley's stability in their marriage allows for a very optimistic and trusting viewof relationships, love, goodness, etc.
3) What do you think about the fact that we rarely see the entire Weasley Clan together? Is this just "bad fortune" or is there something askew with the family dynamic.
I don't really think it has to do with either so much as the fact that it's 9 people across a wide age span all leading different, busy lives, especially with the two oldest sons who are in different countries normally altogether. Just getting 9 people together isn't an easy task.
4) How big an impact did Percy's abandonment of his family from GOF to DH have on his siblings? We've seen that Arthur gets quietly angry and Molly gets tearful. Is there anything Percy's fellow siblings could have done?
It made, at least as far as Percy's younger siblings, extremely angry and feeling somewhat betrayed. I don't think their antagonization of Percy helped the situation but I'm not really sure they could have done anything else- and their reactions were understandable. Maybe Bill or Charlie, whom as older Percy may have respected more, could have tried to talk to Percy, but Percy was definitely a Weasley in stuborness as well- he wouldn't have come back until he was ready to come back.
5) The Weasleys were like a real family to Harry. What's your view on this given that there were already 7 kids in the family already.
The Weasleys are tight-knit but they're a big, tight-knit family, so there is room for Harry to fit in as a sort-of adopted son. The Weasleys are, in a way, Harry's surrogate family, but there is still a definite disconnect- he's a close family friend and maybe something along the lines of a favorite cousin but he's also definitely not a Weasley child. And the fact that Harry is the orphaned Boy-Who-Lived probably does make a difference- he seems to stay with the Weasley's frequently as Ron's best friend (in a way so does Hermione) but you notice that even though Ron is certainly not the only son he seems to be the only one who has friends living over as far as we know.
6) If you filled out the poll above, why was the character you choose your favourite?
I think Fred and George are probably my favorite, followed by Ginny and then Bill.
7) Who are least alike in the Weasley family? Who's most alike? Is there an element of peer pressure on those who are least like the others? Who's the most misunderstood?
Percy and either the twins or Ron- probably the twins. Well the twins are most alike, and then I thought Bill and Charlie or maybe Bill and Ginny. Yes, especially on Percy, who is most misunderstood.
8 )Given Arthur doesn't seem so highly motivated, do you think that his children are "over achievers". The have been very successful in their fields and indeed in school (think quidditch captains, head boys, prefects etc). If so, where do they get this drive?
Every child rebells against their parents in one way or another- I think the Weasley children's ambition comes from a combination of wanting to be different from their parents, from wanting to succeed in order to prove something about their financial status (think of how Ron is ashamed that he is poor) and from wanting to distinguish themselves from their many siblings.