Apr 17, 2018 - 12:20 AM
The train->bus->train changes due to construction are completely painless, and there's even signs on the train that say "connections guaranteed" -- see my post here for more info: www.myswissalps.com/fo rum/topic/golden-pass-line-during-construction
As for the other changes (Spiez, Zweisimmen, Montreux), they're all also relatively straightforward. The one thing to note is that many stations don't have elevators/lifts, but most have ramps if stairs are a problem for people in your group. In most stations, at the end of the platform (terminal stations) or in the passageway below the platforms (where the stairs/ramps lead). there are many digital displays showing the next few trains and what track they're on. From what I remember, all three of these stations are relatively small (only a couple platforms each), so the changes were quite quick. The MOB schedule I linked to in the prior post shows the minimum connection times next to the city name where you'll make connections (the little numbers inside a box).
That said, my GoldenPass journey from Montreux to Zweisimmen was delayed (I assume the bus transfers were built into the schedule but we had some long stops at 'optional stop' stations), so we missed the direct train we had planned for from Zweisimmen to Interlaken and had to take the next train via Spiez. Since you have a flight to make, I would make sure you're planning to get to Geneve Airport with sufficient extra time that you'll still be okay if you miss one train and have to take the next. There are trains from Zweisimmen to Montreaux roughly every hour (not all Panoramic) and two trains an hour from Montreux to Geneve, so maybe leaving 1.5-2 hours of wiggle room in your schedule would be wise, in addition to however early you would otherwise arrive at the airport, though others who are actually from Switzerland may be able to advise better. I haven't flown to/from Geneve airport, so I'm not sure how difficult/easy the train to terminal connection is, so hopefully others can comment there.
I do think the ride is worth it, but I would definitely leave enough flexibility in the event you miss your planned train somewhere. Also, install the SBB app and you can always keep an eye on what your options are for next trains if needed (though you'll need cellular data, or the free wifi at stations)