heres some boring maths for you...
I used WMO for ever! and was recently sent a steelseries sensei to try out.
I wanted to get my old sens and accel exactly on this new mouse but it was allot more tricky than i thought, maybe down to some things steelseries don't tell you about the mouse or maybe coz ther's something i overlooked.
I discovered the phoon website is gone so i used
to do the conversions.

my old settings with the WMO were:
1.5 windows multiplier in xp (notch 7)
1680 wide screen res
103 fov
sensitivity "3.2"
cl_mouseaccel "0.1"

which gave me a 'cm/360' of 27.988980716253444
and a 'real accel' of 0.045353090706181404

I then changed the dpi field to 1000 (which is what I set the sensei to) and the windows multiplier to 1(notch 6), and then tweaked the sens and accel to match these values.
It returned sens 1.92 and accel 0.036 as the equivalents.
but this felt way off when I used them. by switching between the two mice and settings to gradually bring the new one to the same feeling, I came to the settings accel "0.0133" and sens "1.485" which are near perfect.
I'm interested as to why the calculations weren't correct. maybe i was getting negative accel with my wmo before with such a large res? Maybe polling rate up to 1000hz is a factor?
If anyone could shed light on this would be appreciated, cheers!