We will be doing this (HBO) in a couple of weeks (after the construction I think). GPX appears pretty much booked out. Thinking of doing the route on ordinary regional trains changing at Spiez and Zweisimmin rather than the Bern or Visp routes that are generally offered. Will this be possible and have the same scenic views ? Do these trains have first class (especially the scenic bit) )? We will have the rail pass so should not have to worry if this is not a usually offered through route.
We've taken the standard train from Montreaux to Spiez a few times, and been very happy with the views from it. Don't see that the type of train car would make that much difference.
The views from the Golden Pass Express are a bit overhyped in selling the concept as a scenic train. It's not that they are bad views by any means, it's just that if you will have just been taking train rides in the Jungfrau Region around Interlaken those trains will be far more scenic. Just get to Montreux the quickest way possible and enjoy more time at your origin point & at your destination. And yes, SBB trains have first class. You can see times/routes/first class on SBB.ch/en
Perhaps you are traveling on a Saturday, in which case the seats are sold out, but for most other days, in two weeks time from now, there are seats available in second class. Taking the GPX will save you time for this route, 3h 18 vs 3h 47. Is there a reason you want first class?
I actually like this route a lot, it is scenic rural Switzerland at its best. Very pastoral and peaceful views. Approaching Gstaad from Schönried is the postcard view (and the one they use in their advertisements) - best seen from the right hand side. If you are not sitting on that side it can be worth just walking to the nearest door so that you can look out/take photos of the view from that side. I have also walked this section several times and can highly recommend it as an easy, enjoyable hike.
The view down to Lake Geneva and Montreux/Lausanne area at the end of your journey is also very nice and always a fun surprise after exiting the series of tunnels before that.
But everyone has their own preferences, it is just a matter of opinion. The weather also plays a big part, as it usually does for these things. Someone might have taken it in poor weather and thus has a different opinion of the route than another person might. Views often look better in morning or evening light and less interesting at midday, so that can play a part as well. I usually take an early train, giving me the best chance at nice views as well as lots of time at my destination.
I have done this route many times using the ‘regular’ trains. Again though - first class gives you more room and comfort as far as seating, but not better views, so it is up to you to choose what you prefer. I have always traveled second class.
Yes, the STP covers all of the trains, it does not matter which one you take. You never have to go with the route SBB suggests - they will give you the fastest route, but there are usually multiple ways to get from one location to another.
I've enjoyed that route and have only ever taken the normal trains. I like hearing the children going to school chatting in German then a few km later speaking a combination of French and German and then again a few minutes later only in French.
The scenery is the same and the tracks are the same no matter how fancy or not fancy the trains are. I only use 2nd class - much less local experience in 1st class, and the views and windows are the same regardless.
The marketing of this route has made it a lot more hassle than it used to be! The word panorama seems ot be taking on different meanings. The true Golden Panorama Express is a group of special cars which can be altered at Zweisimmen to run on the different tracks - years ago when orignally suggested they were also supposed to alter at Interlaken and give a direct Luzern-Montreux service but they've had enough problems getting the current arrangement to work.
Using the regular trains means changing trains at Zweisimmen, which is hardly a chore. But if you look closely at the timetable (which has also got more complicated than it used to be...) you will find there is some middle ground.
https://widgets.oev-info.ch/publikation/jahresfpl/120.pdf
those marked atthe top of the column as PEGPX are the new ones which can serve Interlaken. But then you notice those marked for route PE30 which also have the little triangle/mountain symbol which means it has cars with panoramic windows. The little symbols 11-16 are dates affecting service, the list is at the end of the document.