I have the same problem. I use one screen above the other and my vertical mouse pointer speed is about double of the horizontal speed. It's unusable this way.

Now this might be a different bug or not a bug at all, but I noticed that the VertResolution and HorizResolution options are missing, even though they are specified in man synaptics:

---------------
Option "VertResolution" "integer"
	  Resolution of X  coordinates  in  units/millimeter.
	  The  value is used together with HorizResolution to
	  compensate unequal vertical and  horizontal  sensi‐
	  tivity.  Setting VertResolution and HorizResolution
	  equal values means no compensation.  Default  value
	  is  read  from  the  touchpad  or set to 1 if value
	  could not be read.  Property: "Synaptics Pad  Reso‐
	  lution"

Option "HorizResolution" "integer"
	  Resolution  of  Y  coordinates in units/millimeter.
	  The value is used together with  VertResolution  to
	  compensate  unequal  vertical and horizontal sensi‐
	  tivity. Setting VertResolution and  HorizResolution
	  equal  values  means no compensation. Default value
	  is read from the touchpad or  set  to  1  if  value
	  could  not be read.  Property: "Synaptics Pad Reso‐
	  lution"
---------------

synclient:
---------------
Parameter settings:
    LeftEdge                = 130
    RightEdge               = 3130
    TopEdge                 = 114
    BottomEdge              = 2005
    FingerLow               = 1
    FingerHigh              = 1
    FingerPress             = 256
    MaxTapTime              = 180
    MaxTapMove              = 171
    MaxDoubleTapTime        = 180
    SingleTapTimeout        = 180
    ClickTime               = 100
    FastTaps                = 1
    EmulateMidButtonTime    = 0
    EmulateTwoFingerMinZ    = 282
    EmulateTwoFingerMinW    = 7
    VertScrollDelta         = 77
    HorizScrollDelta        = 77
    VertEdgeScroll          = 0
    HorizEdgeScroll         = 0
    CornerCoasting          = 0
    VertTwoFingerScroll     = 1
    HorizTwoFingerScroll    = 1
    MinSpeed                = 1
    MaxSpeed                = 0.1
    AccelFactor             = 0.1
    TrackstickSpeed         = 40
    EdgeMotionMinZ          = 30
    EdgeMotionMaxZ          = 160
    EdgeMotionMinSpeed      = 1
    EdgeMotionMaxSpeed      = 311
    EdgeMotionUseAlways     = 0
    TouchpadOff             = 2
    LockedDrags             = 0
    LockedDragTimeout       = 5000
    RTCornerButton          = 0
    RBCornerButton          = 0
    LTCornerButton          = 0
    LBCornerButton          = 0
    TapButton1              = 1
    TapButton2              = 2
    TapButton3              = 3
    ClickFinger1            = 1
    ClickFinger2            = 3
    ClickFinger3            = 2
    CircularScrolling       = 0
    CircScrollDelta         = 0.1
    CircScrollTrigger       = 0
    CircularPad             = 0
    PalmDetect              = 1
    PalmMinWidth            = 4
    PalmMinZ                = 1
    CoastingSpeed           = 20
    CoastingFriction        = 50
    PressureMotionMinZ      = 30
    PressureMotionMaxZ      = 160
    PressureMotionMinFactor = 1
    PressureMotionMaxFactor = 1
    GrabEventDevice         = 1
    TapAndDragGesture       = 1
    AreaLeftEdge            = 0
    AreaRightEdge           = 0
    AreaTopEdge             = 0
    AreaBottomEdge          = 0
    HorizHysteresis         = 19
    VertHysteresis          = 19
    ClickPad                = 1
    RightButtonAreaLeft     = 1630
    RightButtonAreaRight    = 0
    RightButtonAreaTop      = 1737
    RightButtonAreaBottom   = 0
    MiddleButtonAreaLeft    = 0
    MiddleButtonAreaRight   = 0
    MiddleButtonAreaTop     = 0
    MiddleButtonAreaBottom  = 0
---------------

xinput list-props "ETPS/2 Elantech Touchpad":
---------------
Device 'ETPS/2 Elantech Touchpad':
	Device Enabled (129):	1
	Coordinate Transformation Matrix (131):	1.000000, 0.000000, 0.000000, 0.000000, 1.000000, 0.000000, 0.000000, 0.000000, 1.000000
	Device Accel Profile (258):	1
	Device Accel Constant Deceleration (259):	2.500000
	Device Accel Adaptive Deceleration (260):	1.000000
	Device Accel Velocity Scaling (261):	12.500000
	Synaptics Edges (283):	130, 3130, 114, 2005
	Synaptics Finger (284):	1, 1, 256
	Synaptics Tap Time (285):	180
	Synaptics Tap Move (286):	171
	Synaptics Tap Durations (287):	180, 180, 100
	Synaptics ClickPad (288):	1
	Synaptics Tap FastTap (289):	1
	Synaptics Middle Button Timeout (290):	0
	Synaptics Two-Finger Pressure (291):	282
	Synaptics Two-Finger Width (292):	7
	Synaptics Scrolling Distance (293):	77, 77
	Synaptics Edge Scrolling (294):	0, 0, 0
	Synaptics Two-Finger Scrolling (295):	1, 1
	Synaptics Move Speed (296):	1.000000, 0.100000, 0.100000, 40.000000
	Synaptics Edge Motion Pressure (297):	30, 160
	Synaptics Edge Motion Speed (298):	1, 311
	Synaptics Edge Motion Always (299):	0
	Synaptics Off (300):	2
	Synaptics Locked Drags (301):	0
	Synaptics Locked Drags Timeout (302):	5000
	Synaptics Tap Action (303):	0, 0, 0, 0, 1, 2, 3
	Synaptics Click Action (304):	1, 3, 2
	Synaptics Circular Scrolling (305):	0
	Synaptics Circular Scrolling Distance (306):	0.100000
	Synaptics Circular Scrolling Trigger (307):	0
	Synaptics Circular Pad (308):	0
	Synaptics Palm Detection (309):	1
	Synaptics Palm Dimensions (310):	4, 1
	Synaptics Coasting Speed (311):	20.000000, 50.000000
	Synaptics Pressure Motion (312):	30, 160
	Synaptics Pressure Motion Factor (313):	1.000000, 1.000000
	Synaptics Grab Event Device (314):	1
	Synaptics Gestures (315):	1
	Synaptics Capabilities (316):	1, 0, 0, 1, 1, 1, 1
	Synaptics Pad Resolution (317):	32, 32
	Synaptics Area (318):	0, 0, 0, 0
	Synaptics Soft Button Areas (319):	1630, 0, 1737, 0, 0, 0, 0, 0
	Synaptics Noise Cancellation (320):	19, 19
	Device Product ID (247):	2, 14
	Device Node (248):	"/dev/input/event7"
	MaxSpeed (504):	0.100000


Note especially that the capabilities: 

Synaptics Capabilities (316): 1, 0, 0, 1, 1, 1, 1

They specify that the horizontal and vertical resolution can in fact be set (the last two "1"s). However the parameters are missing from xinput and I can't set them. Setting "Pad Resolution" (317) is impossible because it's readonly. So the mechanism to compensate resolutions as specified in the manpage is completely missing. Could this be related?

I'm using xf86-input-synaptics 1.6.2 built on Oct 5. 2012.