I recently used the Regiojet train service from Prague to Ostrava in the Czech Republic. It was the middle of summer, hot, but I was able to find a seat on the train without a problem using the Regiojet website I booked my ticket in 2 minutes. There is also a Regiojet app you can download on your phone. The main website is easy to navigate and comes in 5 different languages.
At the Prague main train station, or hlavni nadrazi, it was a little bit confusing to find the right platform. I found out later the electronic board does not post it until 15 minutes prior to the train arrival. Be on alert and follow the crowd to the appropriate platform. Regiojet trains (and busses) are easy to spot as they are in a bright sunny yellow color. This differentiates them from other trains which helps you, the traveler, get to the right train.
It was easy to find the car and my seat in business class which provides reclining leather seats, free wi-fi, water, coffee, and magazines. An attendant comes around to offer snacks such as salads or sandwiches all are very inexpensive averaging under $10 USD. Add that to a ticket that costs less than $20 USD round-trip for the discerning budget traveler.
The RegioJet was a smooth train ride. Very comfortable and relaxing. I had a single seat against the window. There are however, 4-seaters, or closed cabins for families or groups. I got a great view of the countryside the whole way to Ostrava. I was served free water and had free Wi-Fi. Later, the attendant came around to offer snack choices, such as a light salad or sandwich, juice, coffee or some other type of drink. It was just like being on an airplane except no turbulence. There was no worries about language translation difficulties either.
For me it was a seamless experience using RegioJet and I would recommend it as the ticket costs are very reasonable. The only caveat I have is to warn you to learn the Prague main train station layout and how to find where your platform is. In worst case you can walk over to the RegioJet counter where they will be happy to help you. I wish I had found them sooner but oh well, I did learn how to navigate the Prague train station which I chalk up to traveler experience.