Note you can still get the "splash-proof" version for less $$. I just very recently purchased a Thermapen for myself. I was fairly in the same boat with you - is it really worth it? It depends upon what you commonly cook, or even how much you care about things you only occasionally cook. But also, keep in mind that it's not limited to use in the kitchen - do you have other things for which a good temperature reading is important to you?
My motivation for getting one was candying hot peppers. I've candied them in the past but wasn't thrilled with the outcome. Yes, I had an inexpensive candy thermometer that I used in the past, but again, I was not thrilled with the outcome. The Thermapen is so much faster, I was able to have much more control over the process, and was extremely pleased with the outcome.
That aside, we all have strengths and weaknesses. Some of us are pretty darned good at judging, for example, when a steak is perfectly cooked to our liking. For others, however, this is a continual mystery. The time it takes for a standard meat thermometer to register can be sufficient to over-cook the meat (according to one's preferences, of course.) I'd suggest that for those who can't figure out when a steak is just right for them otherwise, something like the Thermapen is a good, if pricey, choice.
Totally depends on the individual.