Sure thing brother,

Play around with the baud rates and see what max data speed you get. 250K would be awesome! but I think some sought of hardware hand shaking is needed to get up to those speeds. Hahaha

Anyway, first step I think is to increase the buffer size form 1 char to as DT said, about 64 Chars.

Code:
'****************************************************************

    INCLUDE "DT_INTS-18.bas"     ; Base Interrupt System
    INCLUDE "ReEnterPBP-18.bas"     ; Include if using PBP interrupts

'   USB sample program for PIC18F4550 CDC serial port emulation

'   Compilation of this program requires that specific support files be
'   available in the SOURCE DIRECTORY!!  

'   18F*.BAS	Device header files that use the USB libraries
'	CDCDESC.ASM	Descriptor file	for CDC	serial demo
'	JADESC.ASM	Descriptor file	for Jan	Axelson	demo
'	MOUSDESC.ASM	Descriptor file	for mouse demo
'	PBPCDC.INF	INF file for the CDC serial driver
'	USB.TXT		This file
'	USB18.ASM	USB assembler file
'	USB18.INC	USB definitions	file
'	USB18MEM.ASM	USB memory allocation file
'	USBCDC.BAS	CDC serial demo	BASIC program file
'	USBDESC.ASM	Include	file for descriptor file

'   You WILL also need to modify the
'   file USBDESC.ASM so that the only line used is -> include "CDCDESC.ASM"

'   MUST use the 4 MHz xtal for this.
'   this program receives data via usb virtual port then sends out via serial
'   usart.
   
    
    '   USART module
    '   ------------
    Define    OSC     48
    DEFINE    HSER_RCSTA   90h
    DEFINE    HSER_TXSTA   20h
    DEFINE    HSER_BAUD    4800
    DEFINE    HSER_CLROERR 1
    
    '   USB module
    '   ----------    
    UCFG    var byte EXT        ' include UCFG register... Yeah Melabs didn't :o(
    ucfg    =   %00010100       ' enable internal USB pull-up, Full speed USB 
    
    '   ANALOG I/O CONFIG
    '   -----------------
    ADCON1 = 15               ' Set all I/Os to Digital         
    CMCON = 7                 ' Disable Comparator
    
    Buffer    VAR BYTE[16]
    Cnt       VAR BYTE
    B0        VAR BYTE
       
ASM
    INT_LIST  macro    ; IntSource,Label,Type,ResetFlag?
        INT_Handler    RX_INT,_SendUsB,PBP,yes
    endm
    INT_CREATE               ; Creates the interrupt processor
    INT_ENABLE   RX_INT     ; enable external (RX) interrupts
ENDASM

    USBInit
    
    ' Main Program Loop

MainLoop:
    USBService            ' Must service USB regularly
    Cnt = 16
    USBIn 3, Buffer, Cnt, MainLoop
    
    HSEROUT [STR Buffer\Cnt]
    GOTO Mainloop
	
'---[RX_INT - interrupt handler]------------------------------------------------
' PROGRAM COMES HERE WHEN DATA ENTERS THE USART PORT
SendUsB:                        
        HSERIN [B0]
        Buffer[0] = b0
        cnt = 1
    
OutLoop:
        USBService        ' Must service USB regularly
        USBOut 3, Buffer, Cnt, OutLoop
        
@ INT_RETURN
Cheers