Im really disliking this new system, Ive been grinding alot of games out with the attempt to get to the top of my league since it came out and heres my experience. I was placed in my initial division, i went on a 8 game wining streak which was enough to get me promoted, then i went 3-5 over the next 8 games and got demoted. I then went back on a streak and won 8 of my next 9 to again get promoted, then lost 2 in a row and again was demoted.

TLDR; In all, ive gone 18-8 in my recent games and made absolutely 0 progress threw my league. I think this is ridiculous. I hate that i have to string a streak of wins together in a system designed to make me lose half my games to get promoted, and i hate even more that when i manage to do that, it only takes a few loses to lose that progress.

Yah, i just dont get why im getting demoted for going 50/50 or better; In paticular right after your promoted theres a period where you MUST win several games to be 'safe' from getting demoted. Seeing as how it takes a streak of 6-7 games to get promoted, then you need another 2-3 to be safe from demotion, this means to successfully move up the ranks you need to string together 8-10 wins in a row. If your playing near or even slightly below your ideal rank, thats extremely difficult to do. Even worse, is that the MMR system tries to balance you, so if you go on a wining streak, you either A) get better opponents or B) get worse teammates (to balance the overall team MMR) meaning that the longer your streak goes on, the harder it is to continue.

Totally agree man.
I went on a bad streak on my first games, 2-8 and got demoted 2 times.
Now even winning 6 games in a row i will move up only 1 division.
So, get a 50% WR and get a demotion, seems not fair to me.

Was wondering about this myself.
It seems to be very important the order in which you win or lose. This seems... strange and possibly wrong, and definitely encourages demotion.

If you win and lose matches alternatively, you will remain where you're at in Division and LP.
Alternatively, it seems like if you lose 1 match while at 0 LP, you will be one Division lower, with 50 LP, needing to win 3 games in a row to get to promotion eligibility, and then 2 out of your next 3 to get back to the Division you started at. Now I've never been promoted- will I be at 50 LP in the next Division up when I am? Or will I be at 0 LP. Some players are talking about needing to win after promotion to stay in that Division. This would be incredibly imbalanced, requiring you to go about 7/1 to make up for 1 loss.

I got demoted from teir 1 to teir 3 after i got to teir 1 from teir 2. Riot ruined this game

It's based on the skill level of your opponents. In other words if you beat two teams and get 4 points for each, the system knew you were way more skilled. If you lose to a team and lose 20 points, the system thinks you were more skilled and your opponent the underdog. This is why you can win more games for less value and lose fewer games for more value and end up demoted.

The big problem with the system is that it's basically a shiny coat over the old Elo system (Which I liked).

In order to get to Gold from Silver you still need your hidden Elo to be high enough. To prevent people with low Elo getting promoted they award low LP for wins and deduct large LP for losses if their hidden Elo isn't 'good' enough to warrant you being promoted.

While this prevents low skill players going on a lucky streak and getting promoted, it also makes your LP score pretty damn useless as an indicator of how well you are doing.

Essentially the new system will try to get you to the middle of an essentially meaningless list of players and keep you there until your hidden Elo says you deserve promotion/demotion.