Pros
Whilst most of the time you will be lied to, in absolute terms, a lot of what you will be doing or suffering from, will probably be better than you will experience else where. For example, large banks are obviously going to be more hierarchical as an absolute, but they also (largely) don't pretend not to be. I would large suggest reading the below for a more honest view of the company, and if it sounds like a suitable environment for you, go for it, the main issue is its not what you will be told in interviews or recruiting.
Cons
Mostly hypocrisy - below are several examples outlined against Palantir's supposed core values. Flat / No hierarchy: Whilst Palantir will pretend to have a flat structure where merit wins out alone, we also happen to have a concept of "trust circles". Here, people are granted a rating (usually "inner trust circle" or "outer trust circle") which indicates that their concerns are more directly considered by management and directors. In and of itself, I see no issues with this, however, its introduction was never publicly announced, and thus its existence is not widely known, along with how one would ever become part of a "trusted circle". Saving the shire: Most of what you will work on is helping financial and consumer industries secure additional footprint (i.e. expand in new areas or secure additional market growth in new areas). Palantir philanthropic team is one of the only teams to have SHRUNK in the last 2 years (given the company has experience an average of ~90% growth in this time that is even more shocking) with most of the focus being on both insurance, and the oil and gas industry. Additionally focuses on world and environmental health have been actively stopped by leadership, so "saving the shire" is unlikely to be something you do. (Interestingly in the last two year's the company line has also changed from "solving the world's hardest problems" to "solving the world's hardest problems, for the world's most important organisations"). Transparency: It's hard to provide real examples here without breaking confidentiality, but I have received multiple emails titled as being strictly ORCON (originator controlled) to even within the organization because someone needs to "ensure there is a correct framing" (framing is code for white lies; in case that was non-obvious), as well as a lot of active push-back against independent sharing of compensation for "the employees own benefit". Interesting problems: If you are a forward deployed engineer you will mostly be working on data integration and analysis. For reference to those that don't know, mostly this will involved trying to figure out the schema to 1000+ xml files containing "important information" (no schema will be provided by the customer) or correctly joining multiple SQL tables. Whilst there is definitely some joy to be had in writing a nifty tool that figures out likely schema's or predicts row types, after writing the 100th json schema for a particular dataset you realise that the problem is fundamentally uninteresting in and of itself. Once this grunt work has been completed, some are lucky enough to work directly with analysts, however most (because of the vast number of Proof Of Concepts) will be working on creating demoware that appeals to middle-managers that know little about analytics, merely appreciating something with animations and good design.