Scrolling has never been as smooth as Eclair, but on stock EC05, you can clearly see a framerate difference. To me, with the other bugs present (random reboots for example), you might as well just flash the modem and another ROM of your choice that works better.
To go along with that, I like the screen transitions and hardware acceleration Gingerbread brings with the device being "stock".
To be sure I did this right, here is what I did:
Odin to EC05
Enable USB debugging and run CWM 3.0.2.5
Phone restarts and I pull the battery and boot into CWM 3.0.2.5
Wipe data/cache three times
Wipe Dalvik/Battery 3 times
Flash the ROM and restart
Lag is present :'(