I am personally enjoying the new gui and new client it looks very nice. I also do believe that the new client will open up multiple options for Riot Games but there is 1 major problem. And that is lag.
I do not know what happened or why it is happening but while I am in game the client's cpu usage spikes up to 30% from 7%. This is even while it was supposedly closed from the in client setting. This for some reason affects frame rate. I go from a consistent 200fps to 150 spiking down to 100 in teamfights. While under normal conditions this is bearable something feels incredibly off. This lag feels as if im on around 10k ping as damage values and champion animations desync drastically animation cancling and dodging abilities becomes a nightmare and is quite unplayable.
This happened while I was ingame and while attempting to close the client did have improvements it still was causing tremendous lag generally when abilities weer being used.
tldr Good Idea bad execution, This needs to get fixed if Lol is to more forward as a game and rather than randomly implementing the client, the devs should focus on prompting the user to update as this could smoothen the installation process.
I hope this issue gets addressed quickly as in this moment in time people with limited downloads cant afford to try everything riot support have to offer.