The wonderful Mona El-Ghobashy has a new lucid essay at MERIP on Egypt's upcoming parliamentary elections. It is probably the only thing you need to read about it, and answer to why the opposition parties are not following Mohamed ElBaradei's call for an electoral boycott:
The opposition’s choice to participate is not as odd at it seems, for Egypt’s parliamentary elections, despite their serious limitations, are not mere props or stereotypical autocratic rituals of acclamation. They are rare moments of open, if unequal political competition between parties, whose strategic interaction means that elections are far from trivial.
Of course, it was always strange that movements with no MPs or political parties were calling for a boycott, they clearly had more to lose. There's a lot of great info in there.