Pentax k1x0D long exposures (astro photography)

It is yet quite hard to find at least several expert reviews on one of
the 2 new Pentax DSLRs, so behavior at high ISO and long exposure i.e.
5-10-15+ minutes is to me so far unknown.
Is it better or worse than the Nikon's D50/D70 or one of the *ist
series camera?
Is it "improvable" by any means?
(I am not discussing the Canon CMOS DSLR's on this issue, everyone
interested knows they are the best for this kind of work)
The Nikon's workaround for not having the dark frame extracted is, tho'
efficient, quite barbaric IMHO.
If I know well, the D80 has the possibility to disable this dark frame
extraction feature. Also, from what I've read in the K100D's manual,
there is also possible to disable Noise Reduction. If I know wrong,
please correct me. How much improvement does that bring, if any?
The low price on these cameras, together with the overall kit lens
optics, construction and handling quality makes my wish gland drool.