I don't so much have a problem with the way the FBI SWAT teams are dressed as I do with the attitude LEO's seem to take when they do dress that way.
I completely agree that all law enforcement agencies should have the best gear available (sadly this is usually only reserved for federal agencies and large cities).
It's just that when I've dealt with LEO in tactical gear, they all seem to take an overly hostile attitude.
And yes I can speak from experience.
During Hurricane Rita and Ike, local and county law enforcement all took on a more tactical dress code and their attitudes were a direct reflection of their more aggressive equipment.
However, Texas DPS remained in their standard patrol uniforms.

They were still well armed with M4 or Mini-14 style rifles and bullet proof vests, and yes they were still able to perform their duties to the fullest even with the hindrance of pressed slacks.
I feel that because they looked like professional LEO's they were more inclined to help people.
Which they did, I never encountered an instance where a DPS officer was not extremely courteous and helpful.
I cannot say the same however of officers who were allowed to wear the tactical BDU's and such.
While the task of the officers I encountered are completely different than the mission of the FBI and USSS in DC.
I still feel that a LEO's uniform does affect his demeanor towards his job and the public in general.
And maybe it is a good thing for FBI SWAT to have an aggressive attitude towards the public when trying to protect one man.
Again, I have not personally dealt with any FBI SWAT agents or any FBI agents for that matter so my opinion might be far from the truth.
Just adding my 2 cents.
No need to flame, I'm sure most of you don't agree with me.