Generally the advice given on the forum is that the Jerusalem - Tel Aviv train isn't a good option for most people; it's very slow compared to the bus; the station is far from the city center; and unless you're interested in train rides for the fun of it, it's best avoided.
The journey to Tel Aviv took 1hr 25 mins (I left at 9:25 a.m.). The journey back, leaving HaHagana station in Tel Aviv at 15:00 took exactly 65 minutes (I checked the times carefully). That is almost certainly no more than the bus took at that time of day, and quite possibly less.
The train was clean and comfortable. Going there was loads of room. Coming back there were more passengers (and I got on at the third stop in Tel Aviv in that direction), but still absolutely no problem getting a good seat.
I left my car at the station in Jerusalem. There's plenty of free parking. I had less than a minute to walk from my car to the ticket office. There are taxis waiting at the station, so even I hadn't had a car I could have made similar time if I was willing to pay for a taxi. Obviously by bus it would take a bit longer.
For me the journey compared very favorably to the bus. It takes longer to get to the CBS from the south of Jerusalem (and I'm in the German Colony - not that far south). The bus station is crowded and the underground tunnel where you go out to get on your bus has recorded some of the highest levels of air pollution in Israel.
Another advantage over the bus - for some reason, people seem to be much quieter on trains than on buses. A few people made some quiet cell phone calls (including me) but much of the time it was absolutely silent.
Lastly, the scenery is a real pleasure. You go through a lot of unspoiled hilly areas, underneath Palestinian villages, through farmland and up into Tel Aviv.
So my conclusion is that if any of the following apply to you, the train is definitely worth considering:
* You like a peaceful journey even if it's a couple of minutes longer
* You're leaving and/or returning to anywhere in south or west Jerusalem.
* You have a car or you don't mind taking a taxi.
* You're going somewhere in Tel Aviv relatively near one of the three stations the Jerusalem train stops at.
This post was NOT paid for by Israel Railways.