On Mon, 31 Dec 12, Phillip Helbig wrote:
analysis of a gravitational-lens survey is a huge undertaking, and the
fact that the cosmological parameters derived from it agree with those
from much simpler (at least conceptually) tests is a huge argument in
favour of the underlying assumptions being correct.

Agreed, although that "missing matter" is a required part of the
picture should put the spanner in, at least a little.

Another example, Arp and others have questioned the
cosmological nature of some high-redshift objects, particularly QSOs.

Ah yes, I once considered Arp's ideas. As a matter of fact, it helped
motivate my earliest cataloguing efforts back in the late 90's,
because I thought the additional data would show whether Arp's ideas
of QSO patterns around large (NGC-type) galaxies would hold. I
corresponded with Arp on the topic, and we collaborated on my first
paper (http://adsabs.harvard.edu/abs/1999astro.ph..7219F). But the
final outcome was that his model was not supported by the additional
data because the large data would be expected to randomly produce the
numbers of patterns that were found. And as attractive as the concept
of "intrinsic redshift" is, today I believe all quasars are at their
cosmological-redshift distance.

Eric