What would a Democrat victory mean?

Back in February Charlie Cook suggested that it would be more advantageous for the Democrats to fall short of winning either the House or the Senate, as they can escape being implicated in theBush administration's failures and also that with the razor-thin majorities that are all they could hope for they would hardly control either House anyway. Noteworthy too that for all the talk of conservative disaffection with Bush this is an elite not a grassroots phenomenon, the Republicans are in trouble because they have lost support among moderates particularly women, although conservative abstentions could hurt them. How united are the Democrats and how solid would a narrow majority be? They do include Gene Taylor who voted for all four articles of impeachment against Clinton for example, although to give him some credit his district hasn't voted for a Democrat presidential candidate since 1956 and he has been outspoken about Katrina. Good discussion of Democrat factions by left-wing 'progressive' Democrats Chris Bowers, here, here and here, he identified three groups from left to right: the Progressive Caucus which claims 60 Democrat members and 1 independent, the Democratic Leadership Council (DLC) (Clintonites) which claims 40 members and the conservative 'Blue Dogs' with 37. With 202 Democrats this leaves 65 unaccounted for. The DLC members are much less unified in their voting than the others which suggests that the unaccounted 65 can be put in the centre with them. With the Blue Dogs however voting with the rest of the Democrats only 54% of the time on key bills it is clear that a House majority must be highly qualified. Bowers concludes:
Since the average Democrat supported the Democratic position 6.53 times of out a possible 8.00 (81.4%), and the average Republican supported the Democratic majority position 0.24 times out of a possible 8.00 (3.0%), by this measure the average Democratic Representative can be counted on for 6.29 more votes than the average Republican Representative. Considering the 361 vote deficit, in order for the Democratic position to reach majority status, it is thus necessary to replace 58 Republican Representatives with Democratic Representatives in order for the Democratic majority position to reach majority status within the chamber.
However even a one-seat House victory would make Democratic leader Nancy Pelosi Speaker and she is a former member of the Progressive Caucus (she resigned on becoming leader), although she has been accused of modifying her positions to appease more conservative Democrats.