FNMA 5.5% just ticked down under the 101-04 line, which it has done three times today.  If your lender already repriced today, they are not likely to worsen, but if they did not reprice yet, locking is the safer choice.

We'll probably avert the reprice with many lenders, but the directionality with which MBS are moving today makes the risks of floating greater than usual.  If you're a bear on tomorrow's economic data, float.

Many think that the weak Empire State survey from earlier in the week is a good historical predictor for the Philly Fed survey and also point out that Philly is generally weaker.  This would be good for rates.  Take a look at the rest of the data on tap here: http://www.bloomberg.com/markets/index.html?Intro=intro

In general, worse than expected data is good for rates, so use this to draw your own conclusions on locking.  Personally, I'll be floating because I'm generally a bear on the data.  Keep in mind that it is based on the reality versus expectations as opposed to reality versus past reality.  So if you feel that analysts are over-estimating the carnage, weak data can fail to move rates in a friendly direction.  360k for a jobs loss report is fairly high historically, so keep that in mind as you consider tomorrow's outcome.