I've just completed my second pass through the GTD book and learned many new things that didn't make it into my brain the first time because I was being overwhelmed with new ideas...!
My boss is the one that got me hooked on GTD, and we both have come up with the same question/dilemma. How do you handle a situation where you are constantly ACQUIRING more stuff than you can actually DO? It seems that at some point the tide should turn and every so ofter you'd be able to actually DO more and ACQUIRE less...
I suspect that David's comment of "The better you get, the better you'd better get" applies here. I also suspect that such a situation lends itself to evaluating the need for more staff. I personally have added 1.5 staff members to directly help me, which has helped a lot. That's helped me exchange some old stuff for some different stuff.
So perhaps I'm answering my own question as I type along...! But I'd still be very interested in any feedback/thoughts/perspectives from other GTDers in a situation like this... How do YOU deal with the ratio of Getting Things Done vs. Getting Things to Do?