As to which DSLR to buy,
1st of all I think it got to feel comfortable in your hands.
Imagine buying one with the best specs yet doesn't really 'feel' right...and having to hold it for shooting long time..torture..
2nd Budget Limit or Value for money... Pentax and Olympus are good value for the money.
though Nikon and Canon dominates sales but they don't have in body stabilisation (not a neccessity but good to know all future lens will by Image Stabilised when u need it)
3rd Read reviews know about the short comings and stuff, good site is to read dpreview...
for absolute newbie (~S$1500) i'd recommend Nikon D40X or D60 and Olympus E510 or Pentax K100
if for slightly advanced user(~S$2500 and up) i'd reccommend Nikon D300 or Olympus E-3 and Pentax K10D
all weatherproof to certain extents especially for Oly and Pentax..
These were the decisions I was making a year ago and narrowed down the above cameras. In the end I chose e-510 and then to the E-3 for the way it felt in my hand, Dust Busting Efficiency, In-Body Image Stabilisation, Weatherproofing and great legendary but sometimes expensive Lens design.
my next choice would have been a Nikon D200 at the time, budget was a constrain and also the features that i wanted Nikon don't have..
u might notice that i never intro Canon,not that i don't like Canon...my first Digicam as the great A80.. the only body i like is the 1DMkIII......