I think there are interesting parallels to say the least.
I think in terms of international relations, OIF is almost certainly worse than Vietnam, in which we were at least acting to prop up an existing government. OIF seems to be a nakedly offensive operation against a country posing no foreseeable danger to the US (which is even more problematic since, at the exact time we started the war, North Korea was actively and openly developing nuclear weapons and threatening to use them, and any of several other nations in SW Asia had active WMD programs and/or demonstrable ties to terrorism). This has had a grave impact on our relationships with allies, and the current prisoner abuse scandal, unless it is handled aggressively and openly, will aggravate the problem to no end.
IMO the main similarity is that the war is being conducted under tight control and supervision (and arguably hamstrung) by DoD civilians in the US. In Vietnam this initially took the form of requiring all targeting to be vetted through command chains to military and civilian leaders in DC, rather than leaving it to the operators and local commanders who had eyes on target. In OIF, this takes the form of DoD trying to wage the war without allocating adequate manning and resources. In both cases, it inhibits the ability of individual GIs to perform their missions in the theater of combat.