I have had my Tamron 70-200/2.8 for a few months now, and while I am still learning, I can say, without hesitation, that it is a lens you can easily get attached to! The optics are superb, and while the bulk is at times annoying I can find no fault with this lens at it both is a good macro, and a good zoom tele lens, quite in the same leage as Canon's, or Nikon's, offerings, but at a budget price! Adding a monopod to it increases its usefulness, and improves balance, a lot. I have used it with a hefty Metz AF-1 flash on top, and a Manfrotto monopod, which adds up to a fairly heavy package, but it balances much better with the monopod than without (kind of poor man's steady cam .-)!).
Some doesn't like the focusing, as it is a tad slow, and in weak light it sometimes gets the focus wrong, but everything else is so great. Excellent macro lens, too!
But I heartily recommend a monopod with it!
Avialiable for most makes of SLRs, and independent tests have shown it far better optically than the Sigma 70-200!