Just the opposite for me, every update my dev has released for GB on the D1 has been faster than previous releases. Previous as in 2.2+, I use to have to run my device at 1.1ghz+ to get the same performance I'm getting on GB at 600mhz. Huge difference.
If only they could get compcache running tight and smooth. Every rom I've flashed runs great for a day or two then starts to become sluggish and unresponsive. I'm sure it would be great if I'd scale down my home launcher a bit but not a trade-off I want to make.