The campaign filed on the 20th of April, as required by the FEC. Here are some interesting observations at first glance:
[Note: All observations stand true according to the filing as of March 31st 2008]

The campaign's biggest debt remains to be the $5,000,000 loaned to the campaign by Senator Clinton

The campaign, to date, owes Senator Clinton $10,879.89 in interest on the $5,000,000 loan (at a rate of 1.26%)

The Campaign's second largest debt is to Penn, Schoen & Berland Assoc. LLC  
Amount: $4,577,820.61

There's more...

It started last year and now, finally, the last state filing deadline has passed (well, maybe Texas re-opens things).  After 50 states, 435 districts, and lots of cliffhangers, Democrats wallopped the GOP in candidate filing.  The final score was 425 seats for Democrats and 390 for Republicans.

Several significant things stand out.  First and foremost, as Chris has pointed out, the number of filings is a great indicator.  A margin this big is a great sign of victory in November.

Second, not all the free passes Democrats got were meaningless or even close to it.  Three of our 45 unopposed seats were (by congressional standards) close races.  In CA-20, Blue Dog Democrat (that's another story) Jim Costa polled just 53% in 2004 to 47% for Republican Roy Ashburn.  Republicans failed to plate a challenger.  In Kentucky-6, Ben Chandler polled 59% but his GOP opponent pulled out, leaving the seat uncontested.  And in Texas-28, Silvestre Reyes pulled 59% and went unchallenged.
Another ten districts saw Democrats poll between 60% and 69%.  No unchallenged Republican (there are ten) polled under 65%.

There's more...