I've been buying most versions of Trainz as they came out (though I did skip the pretty pointless ones between 2006 and 2009) for just that reason. The catch is that I don't install them until they're sufficiently ready for prime time. I have SP2 downloaded and set aside, and will do the same for SP2HF1, but have no intention of installing either until those who just can't wait report on whether it was a great experience or ate several years' work.
I've also said more than once on this forum that more attention needs to be paid to making the software sufficiently backwards compatible. I've had a copy of Adobe Acrobat 5 (the software, not the reader) which is really ancient by computer standards, but files that I create with it are still readable without problems by the latest Acrobat reader. My copy of MS word will open almost any word document as long as it's in .doc format. Many Trainz users are hobbyists, not gamers, who may work for years on a single route. Having it break because someone decided that they could save a few frames per second by making a basic change is more than annoying; it's motivation to stick with an earlier version of Trainz and stay there, which I'm sure is the last thing that N3V wants.
--Lamont