I bought the old one from a Danish guy who moved on to the new one. Before this I used the non L 85mm
The old one fits me very well especially for the mere 700 I paid for it. But when people say it is slow than this is a little on the nice side of it. The USM takes the sound of focusing away but delivers nothing of the speed you would expect. If you do weddings, frozen poses etc... The AF is fine. If you do picture things in motion... I tried yesterday to shoot my son jumping on a bouncing castle and athletes doing a flic-flac over a wooden box. Used one shot and AI servo almost no keepers. Afterwards I used manual focus locked it in and shot whenever anyone went into the focus trap. Plenty of keepers this way but no chance to change the framing.
In regards to the 135mm: I shot a Peking Opera with the 85mm and the 135mm. With Iso 800 the 135 allowed me to freeze the Kung-fu fights in mid air already (at 2.0) The 85mm allows to do this at Iso 100 but of about 90 shots only 25 had enaugh depth of field or the focus where it should be. The 135 allowed me to focus several times during a flying kick, the 85 barely achieved a single lock. Doing afterwards my homework in Lightroom I first thought my nik software package had an issue, plenty of noise to be removed on the 85mm picks at iso 100 however not a single auto correction attempt from the nik software on anything I had shot with the 135 at ISO 400 or 800