For fun...
Yes, to me it has been. I paid around 330ped for a crafted Valk within a few days of the release, and I have had a blast the entire time. Practical uses, for me, are limited, but the entertainment value makes it well worth it.
I also plan on keeping it a long, long time. Once the TT value gets quite low, it will just become a "parade" car. This makes customizing more logical - I know I could hardly wait to slap on some blue paint I lying around just to have it painted.
The TT value is down from 17 to a little over 14 ped, but most of that was due to a single, car-destroying, AFK incident - a mistake I won't make again. The random hits from mobs don't add up to much - so as long as you get out of the car when you crash or get stuck near them, or when chased by ones you can't out-drive.
I expect that by the time that "parade" time rolls around (based on no pvp, just stray hits from mobs) I will a) have another, cheaper Valk Mk1, and/or b) have the option to get better/different types of vehicles.
As for the cost to drive around, I put 20ped worth of oil in it when I bought it, and it's down to about 6 now. That is cheap for the many hours of fun. I'll drive instead of TP, just because, and I'll hunt and mine and explore more remote places without having to TP in blindly or run for ages.
If you want to use it for PVP, that is a different set of calculations that I don't know enough about, but if you want to cruise around and mostly just have fun, it's a question of how many ped's you can spare.
It's way more fun than an apartment
Miles