It hasn't been bad lately. I run the "Developer Edition" 64bit on Windows 7 at home. It's snappy enough and I haven't been experiencing the random hang-ups like I used to on Nightly 32bit. Chrome still feels faster, but it's noticeably heavier. On Windows XP, the regular releases have been dramatically better than Chrome for the past year or so.
Rather than going "off a cliff" I've been noticing steady, all-around, improvements.