Three words: About bloody time!
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Unless you need to access the immediate Euston/KGX area or the City, I would suggest that Queens Park is a better London terminus than Euston. A trip on the Bakerloo line from Queens Park to Oxford Circus is more pleasant than a trip on the Victoria line from Euston to Oxford Circus. There is also no need to navigate your way through hordes of people and descend multiple escalators before you can even board the tube.
Still, it's a shame that the terminus isn't Willesden Junction, which provides better connections with London Overground (and is especially useful for passengers needing to access south / west London, who currently need to double-back via Euston). I understand that there aren't WCML platforms at the station, but what happened to those (admittedly very speculative) proposals by London Travelwatch to (re)-install WCML platforms at Willesden Junction? The Watford/Harrow/Wembey/Willesden portion of the WCML is a complete mess for local journeys, requiring as many as three changes for journeys of just a few miles.