Hmm, well. I'm not a fan. I guess it's good to hear negatives so you can be prepared, but I propose this.
1. Back Trouble - You will develop back trouble. But then, you will take five minute breaks from hunching and you will start stretching and you will be fine.
2. Weight gain - this might not even happen. You will be stressed, but you will find that exercise will counteract that.
3, Mental Health Problems - you will have moments where you are depressed and anxious. But that will happen no matter what you do with your life. You'll exercise (see #2) and you will be fine.
4. Relationship trouble - maybe. But if it's meant to be, then it will work out. And, again, you will be fine.
5. No more hobbies - ok, yeah, that's just insane. Of course you will still have hobbies.
6. Acute bitterness - if this happens and persists, then you have more things to worry about than grad school. It's not going to happen to most of us.
I know this might have been posted as a devils-advocate situation, but I'm not eager to entertain things that are unrealistically negative. Sure, there will be negative things, but I'm pretty certain that grad school isn't the hell that this blog made it seem. If it was, nobody would do it and it would have disappeared a long time ago.
I'm also sure that a LARGE majority of the people on this site know what they are getting into. And guess what? They are still doing it.