No experience of using them, much experience of using internet.
I looked at the website, really looked at it. The number of possible tours across all those countries is absolutely massive - they seem to be much bigger than RS Travel. Clearly targeting (or preying on) Americans with dollar pricing and a 1-800 phone number, but not an American company because if you scroll down there's their address "Kilroys House , Patrick Street , Mullingar" - so that would be in the Republic of Ireland!
So, I put that address into Google Maps and then switched to Streetview to see how big their corporate HQ is. You can do the same. It's a tiny little cottage. So I put that address as a phrase ( include quote marks) into a Google search. You can do the same. On just page 1 of results this tiny cottage is home to Go Euro Tours, Dreamtrip Scotland, Go Asian Tours, Go Iceland Tours, Go Irish Tours, Go Scottish Tours, GoNewZealand Tours, Go France Tours. And a company call DG Ventures https://dgventureslimited.com/brand/
Adding a bit of european knowledge to the matter, the Go Rail Travel site doesn't mention any consumer protection in case of company failure which an EU company of this sort should have. Nor does it show any Irish company registration details - probably because it's not a registered company. But DG Ventures has at least 5 variants of company registration, sadly Irish records aren't as open as in the UK so I can't check actual people.
So how do you feel now about handing over money (they seem to prefer wire transfers....)?