The train trip Jakarta to Bandung is worth taking just for the sake of it, though a number of Indonesians use it to commute as a traffic free alternative to taking the toll way. The trip itself is 3 and a half hours and winds out through Jakarta kampungs, passed rice fields and then winds up through mountains, valleys and waterfalls. For the best views book seats C-D for the Jakarta Bandung trip or seats A-B for the return Bandung Jakarta trip. This ticket was Rp. 130,000 or slightly less than $15 USD.
Unfortunately the rail operator does not have an online booking facility yet, though you can check the schedule via their website here, if your Indonesian is good enough. It’s important to know that there is several classes of train, some with AC some without, some express and some not and so on, it would be lovely if they labeled these as A,B,C class etc, but they do not. You need to know the name (however, price is an indication too). The executive class carriages are for allocated seating, AC (which also means no smoking) and a TV. Apparently Argo trains are the best, and Trasaka are also very good. The platforms at the station have signs for each type of train, though the staff will assist you in getting to the right direction as well.
However, I have to confess, I had our driver head to Bandung and meet us with our car, so that we did not have to deal with the notorious public transport in Bandung.