Another appendix to the reservations thread, detailing why cd.cz has become my favourite place to buy seat reservations for central Europe;
This really helped me out today when I realised that track works meant the 9-minute change at Ostrava that I had booked wasn’t going to be feasible; unlike at either bahn.com or oebb.at, many (or perhaps even all) reservation-only bookings at ČD are fully refundable.
As well as domestic trains, you can also book most trains in all of Czechia’s neighbouring countries, generally priced at 75Kč each. This is only €0.07 more than at oebb.at, and is usually* quite a bit cheaper than at bahn.com.
Now of course, €3.07 on a train cancellation won’t be the biggest saving you’ve ever made, but it also frees up the seat for someone else to buy; so it’s considerate and ecological too.
Another thing I really like about booking through ČD is that it’s possible to select specific seats even for foreign trains, by typing in the carriage and seat numbers. Although you won’t be shown the seating map or availability, you can usually find it by running the same search on the website of the relevant train operator. I am not aware of any other site that allows you to request specific seats on foreign trains in this way, only vague preferences.
And finally, if you have the ČD app installed and then proceed to log in and buy through the computer, the reservations will instantly appear on your phone, announced by a joyous and exceedingly cheesy steam train sound effect 
What more incentive is needed?
*(unless your journey involves more than one train within Germany on which reservations are possible)
