Yes, my IB quotes were lagging at times. I noticed it most--and most severely--on INVN as it started dropping just after Bush's press conference began at about 3:00 ET. My quotes--both bid and ask--were at least ten cents behind, and maybe 20 at times, on a $15.50 issue. Worse yet, my stop limit order did not trigger even with the lagging prices having met the qualifications (two asks at or lower than my stop election price).
Otherwise, though, IB worked acceptably for me today.