I won't buy a 3D printer. Bit like home printing- I don't bother. If I want printed photos I go to a bureau- their printers can produce much better results than anything I would have at home, and they get to deal with the hassle of jams, clogged heads etc. I have a cheap black and white laser printer for printing casual hard copy.
Round the corner is cheap bureau style 3D printing. At the moment it's expensive, because its still rather exclusive, patents are tied up etc. Big outfits like Hewlett Packard are stepping into the ring from next year, and I think we're about to see the cost of professional machines take a tumble.
Laser sintering is the most practical way of printing strong and inexpensive parts, and I think you will see new machines coming onto the market in the next 12 months.
With regards to the topic of 'is it modelmaking'. In my view, it isn't, just a different skill set, bit like comparing a draughtsman to a toolmaker. Anyone that thinks 3D CAD work is a cakewalk is deluding themselves, and 3D printing throws a few extra hiccups into the equation.
How do you know if something is 3D printed or scratchbuilt? Well you don't, simple as that, any tell-tale signs could me easily masked with careful sanding and painting.
I guess this sort of thing matters more to modellers who like to compete in exhibitions or those who judge the quality of entrants. Looking at it another way, how many modellers avail themselves of CNC machining, waterjet/laser cutting, photoetc. These are all partly automated modelling techniques, and they've been around for longer than 3D printing.