Sigma 70-300mm f/4-5.6 APO DG Macro Nikon-f performance as tele-macro combination?

A few DSLR photography forum said that this lense works well both as macro and telephoto lens, any comment on that? I'm using Nikon D5100, will this lens work on my DSLR? It is said that this lens comes with a built-in integrated HSM, so can it auto-focus on my Nikon D5100 which doesn't have a built in zoom motor? Some of my friends said that Tamron lenses' zooming quality SUCKS, is it true that the Tamron lenses often causes blurring when zooming?

I guess what you need to know is that all true macro lenses have a couple of things in common.

1) they are flat field prime lenses
2) they can shoot at calibrated subject to image ratios of 1:1, 1:2, 1:3 and 1:4

NO zoom lens can do either.

If you need a 70-300 mm lens, then buy what your budget will allow. But do not expect much when it comes to shooting macro with any zoom

A 70-300mm macro lens will be a mediocre zoom and a mediocre macro. The upper level 70-300mm (Nikon or Tamron) is reputed to be very good, and there are some very good prime macro lenses. The Nikon 105mm AF-S VR macro is reputed to be great, and the Nikon 60mm AF-S very close. If you are looking at keeping your budget closer to that 70-300mm macro lens, you could get better quality with a 55-200mm AF-S VR and the 40mm AF-S macro.

As a dirt cheap telezoom it's not bad, especially if you can stop down to f8. As a macro. I've seen good shots but I never could get anything decent out of mine. It was only macro from 200mm onwards and even then it was 1:4 or something like that.

IF you get the motorized version then it will autofocus on your d5100.

Any lens will blur if you zoom while shooting, that can be fun like this

Tamrin makes 2 lenses you may be looking at, the cheap 70-300 which is about the same quality as that sigma and the more expensive 70-300 VC which is quite good and can rival nikon's 70-300

On the lens quality scale I would rate Tamron worst (not bad but worse than the rest) - from worst to best:
Tamron, Sigma Tokina Nikon

The 70-300 Sigma is not a true macro lens (see fotoace's reply) just a lens that can focus over a short distance.