This latest patch has created all sorts of issues.
1) When I pick my masteries before a match it shows the previous one I had selected not the one I just picked.
~~2) After a game it now takes forever to get to the score screen.~~
3) Sometimes I get into an ARAM pre-match screen and everything is blank and I can't see anything but the lobby still works and goes into the game.
4) Latency gets progressively worse every game. Sometimes restarting helps sometimes not. (not sure this is related to the client though)
5) Sometimes skin selections don't work and just pick the skin I had previously selected.
Oh something else - You can't make custom item builds with the new client but it still uses the json files from the old client. So your custom builds work ... you just can't change them easily.
Edit: Looks like the long loading times are for the low spec mode.