John the Pump uses VCarve Pro (he may see this and comment himself). It's very good for engraving loco nameplates and similar. As the name suggests, it can program for a vee shape tool so, by modulating the Z-axis during cutting, it can pull the tool out and get really crisp internal corners. You can program for a normal endmill to do the bulk background cutting, finishing with the vee tool for the fiddly bits. I'm sure it can be used for general purpose work as well.
Its G-code output seems to use G1 commands (straight lines) rather than G2 and G3 (curves), so uses lots of tiny straight cuts when navigating round shapes. Which makes the output a bit hard to read.
I've not used it myself, but have watched John using it and it seems like fun.
I suspect it's quite expensive - John will have earned its cost back many times over on commercial jobs.
I went to Vcarve quite a few years ago after struggling with the free CAM software available at that time. At first glance, it seems to lack a lot of the features that you find in CAD/CAM software aimed at commercial engineering users but there are two things to bear in mind. One is that its primary user base is woodworking, and for most woodworkers the tools available are aimed at that audience. The other is that those tools available are actually very well chosen so that, for example, the 95% of the tools in something like Fusion 360 that you never actually use aren't there to clutter up the interface and generally muddle things. It is much easier to pick up and use than F360 and similar.
Yes, it is excellent for lettering (I have made both house nameplates and a brass master for lost-wax casting club badges). The comment about approximating curves with straight-line segments is misleading. The software comes with a large range of post-processors which is the component responsible for actually generating gcode and some of these will give "straight line" output but for Mach3 and UCCNC (the two systems I use) there are PPs that generate proper curves (G2/G3). Works well.