Yes, I consider this the most fun game I have ever played, closely followed by Fallout NV which is also a big favourite of mine... It is hard yes, and RNG can be a pain, but in fact, it is the RNG that contributes to excitement when it comes to risk and risk-taking. Shall I go forth to the boss with my heroes in somewhat shabby condition and maybe reap the rewards if luck is on my side or die? Or abandon the expedition and lose the invested dungeon cash and get extra stress? Sometimes you are lucky and sometimes less so. But the major part of the game is to learn the mechanics and strategies. It requires heavy investment in experimenting and/or (for me at least) reading, but the reward when you finally master difficult situtations (sometimes made extra difficult by the RNG) is so great. I love it, have played about 100 hrs (!), and I'm halfway to completing a Stygian run. Well worth it if you like tactical battles, management of scarce resources and dark aesthetics.
The game has interesting graphics and an intriguing story. The stort development is logical and seems plausible in the setting, which means that you get quite good immersion from the game, important for playing an RPG. My only issue is that it ends a bit too early, I was surprised to reach the end at the point that I did.
There are a few games that I've bought that were really worth every penny. To me, this is one of them, on par with Resident Evil 4 and Neverwinter Nights 1/2 and some other gems... Perhaps the expansions, especially Old World Blues (the theme is fascinating too) and Dead Money, are even better than the main campaign, which is really good in itself. Don't forget to mod the game, especially graphics mods (like the texture mods) and some balance mods are worth it in my opinion.