OK, my experience with the revised tool
It converted the mapinfo that took me the best part of two hours to convert to the new format manually in less than a second.
enter/exit texts converted (as far as I can tell) properly
The not so good:
GL_Renderer sections, as expected, broke the conversion process slightly. Basically it seemed to read the closing } of the section as a top level keyword, put an = sign after it and everything in the map definition was out of step from that point on. Or, if the GL_renderer section was the last thing in the map, the start of the next map definition was messed up. However, in both cases the effect was limited to a few lines and was easily fixed manually and it is an issue that will simply not affect most people.
In cluster definitions, the word "cluster" was used instead of "clusterdef" giving an "Unknown top level keyword" error when I tried to run the mapinfo in Zdoom. Again, an easy manual fix and most people will not have as many clusters as I do (75). However, this is clearly a bug/typo and if the tool is to be supported it should be fixed.
Something is confusing Zdoom's ability to report which line the error is on (perhaps the way that comments get moved around or the fact that additional line breaks seem to get added near comments). This hampered the ability to track down where the errors were. Zdoom would tell me that there was an "Unknown top level keyword" on a certain line but the actual error could easily be 100 lines away from the reported line according to my text editor. When I did the manual conversion, the line numbers were always reported 100% spot on and were a great help in tracking down the errors.
So, overall, 2 hours of work was reduced to a split second of conversion followed by about 5 minutes of tracking down minor errors. I'd say that was an improvement.
And finally, not related to the tool, I noticed that Zdoom is still reporting unknown map keywords in black in the startup window. Do you want a separate bug report for this in the bugs forum?