Take my opinion as one of the more informed. Why? I have been leasing one since Dec 2010. Attempting to compare to the GN vs New Regal isn't to bright
Its not a muscle car; its a sport sedan.
It's a rebadged Opel Insignia, which has a AWD 325hp v6 Turbo version in Europe called the Opel Insignia OPC. Buick is trying to get that here but the Green forces in GM are resisting that.
the I4 direct INJ VVT engine has 220 hp w/ 258 Ft LB torque; but people have complained it only does a 16 sec quarter mile. But did they know the car weighs 5250 lbs?
Part of that is because the long list of standard features. Features that post as optional on a lot of its competitors lists.
And the other reason is because is it's made to be a very safe car, (the side impact airbags coming as standard equipment).
I get 23 MPG city, (and I'm a "spirited" driver).
And it handles very well, an 80''s G body could only dream it could handle curves and turns like the 2011 TR.
So it may not be the muscle car of the 2000's and it wasn't meant to be ; but it might be a glimmer of light in Buick's future like the 82 carbed Turbo Regals were in the early 80's.