I'm all for the Red Line Extension (really, any expansion in rail access is a win in my book), but I do think there are other projects that may (or may not, this is my opinion after all!) be more deserving of scarce transit funding. The circle line would be my top priority if I had any pull with the RTA. We have pretty extensive rail infrastructure in this city, but its very much hub and spoke; if I want to transfer onto other lines, I either need to go downtown or take a bus. The Circle Line adds maybe a few miles of additional rail, but makes connections so much more seamless that it adds value to every single existing CTA line simply by making every line more accessible to one another. The potential Metra tie-ins is icing on the cake.
Source: chicago-l.org
That said, I think Metra and the CTA (and to a lesser extent, Pace) need to stop competing and start working together. Combined, they have a much louder voice than they do now fighting amongst themselves. The RTA needs to simply be given total control of finances and leadership, and each of the existing agencies simply become an arm of a much bigger transit authority. The chances of that happening however are pretty low.