Ah, to heck with all the numerical rationalization
, we can always find a way to convince ourselves to buy and carry any fine lens.
1. the 50-135 feels and acts like a series of prime lenses. the optics are just stellar. Its not expensive when you consider its cheaper than a coupla brand new primes.
2. It makes even my half-assed compositions look good
3. when i first got it, i disliked the long hood, and even bought a short rubber replacement from adorama. but then the brilliance of the hood convinced me, the long hood keeps every stray bit of light off the lens, and if its raining - its my rainy lens - it keeps the rain drops off the outer lens which will ruin any shot. wondeful lens in the rain as long as you don't point it upwards.
4. has great bokeh
5. I wouldn't call its a sports lens unless you were in closer than usual, or a wildlife lens. in many ways its perfect for outdoor plays, special events and indoor/outdoor theatre, which is what i bought it for. perfect also for many cityscapes. tons nicer to carry around than todays 70-200
The bad: Its focus speed is a little on the slow side. i compensate for it by anticipating the area where i think the stage action may be occuring and use the af button rather than focus on every shot. works fine. in 3 years, i've had no problem with the sdm, if it failed, i'd get it fixed. its silent which is a plus for indoor shots.
Carrying on a trip? Depends on the trip. If it was a hiking trip, i'd carry a series of primes. around town, i carry it a 21 and a 35. or a tamron 28-75.
If i could only have one lens, this is the one.