Yeah, to be honest my primary bike is an '03 Speedmaster, and I can tell you from experience that it'll blow the fenders off a Sportster 1200. It's not quite as quick off the line, but after about 20ft it's all over. (Then again, mine is far from stock.)
I'm told that Triumph really screwed the pooch with the Scrambler, though. I agree with the other folks here -- I cannot for the life of me figure out why they'd de-tune the engine.
As for why folks ride these bikes? Well, my last bike was an SV650, and I loved her dearly, but honestly the Triumphs have more... soul. Sounds cheesy, but I finally understand the appeal. It's not about going faster or cornering better, it's about having more fun. *shrug*
I still get to surprise some unsuspecting sportbikers, tho.
--Jaeger