For reasons I can't go into, I can't really make any political arguments. However, I can present certain facts.
Think Progress already has the key points of the President's speech tonight.
http://thinkprogress.org/katrina-speech-tps/
Now, the Commissions that this will be modeled after are:
the 1973 Watergate Committee
the 1987 Iran Contra Committee
the 1994 Whitewater Committee
the 1995 Whitewater Committees and
the 1997 Campaign Finance investigation.
However, other than the 1994 Whitewater Committee, EACH COMMITTEE WAS ONE POLITICAL PARTY INVESTIGATING THE OTHER. 1973 and 198 had Democratic Congresses investigating Republican Presidents. 1995 and 1997 had Republican Congresses investigating Democratic Congresses.
Finally, the 1994 Whitewater Committee was attacked as so toothless that political pressure led to both the change in Congress and the appointment of an independant investigator.
I'm sure you all have your own takes, so I'll just leave that for commentary.