There is an excellent Talking Points post on Iraq. John Marshall supports regime change like me and we share the same kinds of doubts about Bush's planned invasion. He articulates them far better then I could:

There's also an issue people don't like to talk about, but which is an undeniable reality for many. Military action is easier to contemplate if it's being planned by political leaders who you support and whose values you share. One might say this is mere partisanship, agreeing with what politician X wants to do because he's a member of your party or vice versa. And there's always some of that. But it runs deeper. Following political leaders into war requires a deep measure of trust on a variety of levels: trust in their judgment, trust in their analysis of factual information that can never be shared with the public, and so forth. If your general sense of an administration is that they're not trustworthy or that they don't share your values it's difficult not let that color your opinions. Of course, to some degree it should color your opinions

I have the same problem. I really would like the US to remove Saddam from power, but...I'm not sure if Bush can do it, or at least do it right. The administration is very abrasive with other nations and has a history of wasting international political capital on brain dead moves to satisfy domestic political interest groups. The Steel Tarriffs, irrational fear and loathing for the International Criminal Court and the Canadian Lumber Quotas are just a few symptoms of this disease. Such short sighted and politically motivated moves have cost us international support (or at least getting that support very difficult). Multilateral support (for me, unlike many others on the Left) is a practical problem and not a moral one, however, it is a big practical problem. The Europeans frequently help the United States out with nation-building (Exhibit A: The Balkans, where the Europeans have been performing peacekeeping missions. Interestingly enough, during the 2nd presidential debate, W. denied that Europeans were pulling their weight ), but without international support, the rebuilding of Iraq will have to be done on our own dime. Given that all the costs of reconstruction in Iraq will be on us, I fear that Iraq won't be rebuilt at all or at least in a very half-assed way, a la Afghanistan. Which brings us to the larger issue, the problem is that this administration is isolationist at heart and doesn't really want to be involved with the rest of the world (even though Isolation has clearly been a fantasy since World War One). This has been true from the very start and failing a sudden attack on conscience; it'll be true to the very end.