Bagger, everything looks normal - until the ground isn't there when
you expect it to be; seems like you flare about 1-2 feet higher.
There is an abrupt arrival once your fully-held-off approach leaves
you will the flying qualities of a brick and too much altitude below
you. With the addition of a contaminated airfoil making stall speed
higher. carrying a couple of knots/mph/kph/furlongs per fortnight and
flying it on seems prudent.

Details mentioned at:
http://www.nappf.com/nappf_aero_medi...%20in%20Flight

From the Canadian Tansport Canada Aeronautical Information Manual
(AIM), Airmanship, Section 2.5:

"An error in vision can occur when flying in rain. The presence of
rain on the windscreen, in addition to causing poor visibility,
introduces a refraction error. This error is because of two things:
firstly, the reduced transparency of the rain-covered windscreen
causes the eye to see a horizon below the true one (because of the eye
response to the relative brightness of the upper bright part and the
lower dark part); and secondly, the shape and pattern of the ripples
formed on the windscreen, particularly on sloping ones, which cause
objects to appear lower. The error may be present as a result of one
or other of the two causes, or of both, in which case it is cumulative
and is of the order of about 5° in angle. Therefore, a hilltop or peak
1/2 NM ahead of an aircraft could appear to be approximately 260 ft
lower, (230 ft lower at 1/2 SM) than it actually is.

Pilots should remember this additional hazard when flying in
conditions of low visibility in rain and should maintain sufficient
altitude and take other precautions, as necessary, to allow for the
presence of this error. Also, pilots should ensure proper terrain
clearance during enroute flight and on final approach to landing. "

The AIM is now online, and a good reference for things like this.

Dan