135mm Legacy Lens opinions wanted

I've recently bought a Carl Zeiss Jena 135/3.5 (M42 mount) and I'm pretty happy with the results. It is a bit pain in the ass to focus because of my shaky hands (too much coffee or alcohol I guess ). But apart from that it is great. One thing to note is that at 3.5 it is a somewhat dark lens so you need good lightning conditions to use it (I'd say - daylight). Otherwise tripod + long exposure is a must (I have the first nex 5 wich is not so great at ISO higher than 800)