Our USB LCDs use "Virtual COMM ports" which are great since all software written for the serial LCDs will work with the USB LCDs. The transfer still takes place at the 19200 baud.
Really though, that is fast enough--the transfer rate is typically not an issue though. From this post:
Do keep in mind that the speed is really a non-issue. The bounding factor with either the serial or parallel LCDs is the response time of the fluid--not the interface transfer rate. A serial LCD operating at 19200 baud can update the entire screen of a 20x4 at 24 frames per second, which is 41mS per frame. The response time of the LC fluid is typically around 100mS to 150mS.