When I was at Brobeck, Phleger & Harrison LLP we accepted how "the street" (our clients and referral resources) acknowledged us and changed the logo, not the name, of the firm to simply, "BROBECK". Unfortunately, the tag line came back to haunt the ragged survivors - "When your future is at stake". At Deloitte & Touche LLP the street name we honored in the logo change of 2003 was "Deloitte." It was the name all of our clients and business community used to talk about us.
At Rutan & Tucker LLP we were known verbally as just, "Rutan". The logo change was easy. Oddly enough, in historical archives I've discovered that in 1965 (or thereabouts) the firm seriously considered shedding all of the partner names (seven at the time) to just be "Rutan", but it was voted down in favor of a two-name moniker.
It seems that a lot of attorneys like big, long, multi-part names for their firms. While the legal name of a firm can be as big and bodacious as you please, creating an identity has always been about keeping the message simple.
As a competitor I appreciate that so many firms keep their long name as their street face -- it helps my efforts to stand out with a strong and community friendly identity. But just in case you're listening and hope to create meaningful change in your brand, dump the "alphabet, LLP". Let the street know you're listening.