Just got a Manfrotto 055XPROB w/ a Manfrotto 496RC2 head and have had no problems with it. However, the heaviest glass I have used on it so far is the 17-55 2.8IS, not had a chance to put a 70-200 or any long zooms on it.
Holds up very well with my mid zoom, and absolutely love the legs.
Would you strap this tripod on a backpack for a hike? Is it to heavy or long for a hike?
What head are you using?