It's pretty awful in general: it has lots of things huge corporations want that might, but many of those things are bad for the average person.
The biggest offender is the "Investor-State Dispute Settlement" stuff, which is what would allow international investors (the vast majority of which are multinational corporations) to sue countries for doing anything that harms their expected profits. These sorts of arbitration panels made sense to protect multinational corporations from getting their assets in a country seized by the government without any compensation, but in countries with reasonable legal systems there is no need for them and they only give those corporations a huge advantage (largely because the people who make up those panels tend to be corporate lawyers with plenty of incentive to rule in favor of corporations they might work for in the future, similar to how US banking regulatory bodies made up of former and future bankers tend to be horrendously biased toward banks) that undermines a nation's sovereignty.
This guy explains how it's nonsense better than I just did.
The TPP also imposes some pretty shitty rules for intellectual property protection. Here's a quick overview of the bad things outlined by the Electronic Frontier Foundation, which you can read in full
here. The TPP outlines some set in stone protections and rights for the owners of intellectual property while only suggesting and encouraging that rules be put in place to protect users (such as the rules the US has now governing fair use of copyrighted material), which means countries that are shitty about their copyright laws can still be shitty. Oh, and if they ever want to move toward being less shitty, unfortunately for them intellectual property matters are governed by the above ISDS thing which means that they can be sued for doing so because it would cut into their long term expected future profits from their copyrights. The TPP declares that the length of copyright ownership in membership nations is life of the creator plus 70 years, which raises the current term in most member nations by 20 years and that doesn't actually do anything productive for creators and innovators. The TPP makes it illegal to bypass DRM even if you're not violating copyright when doing so, which means even things like bypassing a Blu-Ray disc's DRM to create a digital copy of a movie you bought a physical copy of is now totally illegal even if you never share it with others. The TPP's rules on criminal enforcement and civil damages for copyright infringement includes the possibility of jail sentences for any large scale copyright infringement, not just those done for commercial gain as is the standard currently, and it includes the ability for governing bodies to destroy anything that was used to violate copyright or bypass DRM, meaning if TPP comes into effect and you get in trouble for sharing copyrighted files then your computer might be confiscated and destroyed for it. There's a thing in the IP provisions placing very harsh criminal penalties on anyone who gains "unauthorized, willful access to a trade secret held in a computer system" that are for some reason much harsher than the penalties for attaining that information in non-computer ways, and there is no exception for whistleblowers who access or spread such information even if it's something the public should definitely know. The TPP will force most member nations to adopt something similar to the US's shitty DMCA notice-and-takedown system for enforcing copyright claims online, which basically forces internet service providers to become copyright enforcers. The IP stuff is overall pretty shitty for average users, but pretty nice for big corporations that want to hold on to their copyrights for dear life and severely punish anyone who dares to violate it.
Just that shit above is bad enough, but there's more. It imposes stronger limits on how long pharmaceutical companies can hold copyright of life-saving medicines, which means it'll take longer for medical aid groups to get affordable generic versions of them to people in poorer nations, which means it will literally result in unnecessary deaths;
here's a statement on this from Medecins San Frontieres (also known in the Canada and the US as Doctors Without Borders). There are some other things that seem to have bad implications for online privacy, and one thing that might allow member nations to enact mass surveillance on other member nations due to a requirement to give telecommunications providers access to international submarine communications cables, but these are more iffy and kind of depend on interpretation.
And all that doesn't even address the concerns of the negative effects that might come from the actual "free trade" aspects of the TPP. It's just a huge pile of shit and I hope that the legislatures of the member nations end up denying it, though it looks rather unlikely at this point.