Right. I have the problem with my Magic Trackpad when Time Capsule backups kick in on my 13" Macbook Pro (2010 edition). The Trackpad becomes unusable as the performance stutters.
My Macbook Pro is elevated about 8 inches off of my desk by a Griffen Elevator Laptop Stand to prevent neck cramp. In addition to the trackpad, I'm also using the Apple wireless keyboard.
http://store.apple.com/uk/product/H2619ZM/A
Work-Around:
The problem appears to be the strength and placement of the blue tooth antennae in the MacBook Pro. There appears to be a blue-tooth blind-spot between the 4 to 5 o'clock angle to the right (and possibly below, as I'm using a stand) of the Macbook Pro. If I shift the Macbook so that the Trackpad is directly in front of it, the problem goes away. Likewise if the trackpad is sitting to the left of the Macbook Pro, the problem goes away (so possibly not a problem for left-handed users).
The right-side stuttering problem is more pronounced when the Macbook Pro is elevated on the laptop stand, than when it is at the same level as the TrackPad where it becomes at least usable, but still a bit noticeable.
So, if experiencing this problem, try moving the trackpad's position in relation to the Macbook Pro so that it is either somewhere directly in front of the laptop or to the laptop's left-hand side (7 to 8 o'clock angle), then once the Time Capsule backup has finished move the Trackpad back to a comfortable position.
Not the best solution, but it keeps me sane.