Like Jonathon, I'm a former competitive powerlifter, so I obviously believe strength training has value.
I still haven't the slightest idea what Lynn means by "two .... unrelated complementary activities", but then again, I'm not the smartest bear in the woods.
IMO, if someone wants to strength train to improve aikido, of course it can be done, but one has to train properly (with the goal of improving their aikido firmly in mind).
<gets on soapbox>
The majority of strength/weight loss/health routines are focused on appearance NOT on improved functional performance. Most routines in magazines are based on bodybuilding routines and imply various machines/facilities and recommend different suppliments. That's not necessarily the way a particular athlete should prepare for the physical demands of their activity.
As an example, powerlifters often refer to bodybuilders as having a body "for show, not for go" (in other words, bodybuilders look like they are in fantastic shape, but simply do not have the explosive strength or limit strength as powerlifters. Neither group would fare well in swimming/gymnastics/running etc.... Decide what you want and train for it.