I don't agree that any calibration needs to be done for each individual disc. I have an XBR950, and I suspect the XBR2 is similar.
First, do you use an HDMI connection for the BDP-S1?
Did the calibrator specifically calibrate this input?
If both answers are yes, you're all set. I've found that all digital video connections meet the same standards, and once the specific digital input is calibrated correctly, it's correct for all devices connected to that input. In addition, any other digital input, whether it be HDMI, DVI, or iLink (Firewire) can be properly calibrated by matching all service menu values, and user menu values to that used for the calibrated input.
One note of caution.... If you notice that Blu-ray discs don't look quite right, you may have the problem of the video setting for HDMI ouput on the BDP-S1 reverting to an ouput setting designed for using it with an RGB input each time the unit is turned off. This is evidenced by slight oversaturation of colors, and black level being a bit off.
The easiest way to check this is to turn the unit off, then back on. Then go to Video Setup in the main menu. Select "YCbCr / RGBPC (HDMI)". Then find "Y, Cb, Cr" which should be the correct setting if you're using HDMI-HDMI for the connection to your XBR2. "Y, Cb, Cr" will show as already selected if you selected it previously, but select it again anyway. If the screen goes momentarily black when you make this selection, then your BDP-S1 has the problem, but the output mode (and picture quality) will now be correct until you again turn off the BDP-S1. If the unit has this problem, you must repeat this procedure every time the unit is turned on. Firmware version 1.50 has not corrected this problem for me.