Agreed. For most rooms (with at least a 12' width and speakers placed at/near the back corners) film soundtracks/concerts sound better with 7.1 almost all the time. My preference is usually the SB effect from a THX Ultra2 settings (or Select2 if you have an SC-05) with movies. For most TV sourced 5.1 Dolby Digital presentations I prefer Dolby EX and PLIIx decoding over Ultra2 though.
The only exception I can think of is on some SACD/DVD-A recordings native 5.1 is better since the matrixing alters the placement of some musical reflections/instruments and mixing choices. Other than for these rare instances/sources 7.1 is superior even when it's matrixed. I find it produces a far far more immersive experience on most soundtracks.
In essence SBL/SBR act as a rear center. Would you listen without the front center? Heck no. Why listen without the rear fill and central sound effect that mimics that positionality? That's 6.1's or 7.1's true benefit.