When the client changes were first made, there was some lag when typing out chat messages. Colin and I corrected that issue several days ago. Update your client, if you haven't done so already. None of the other changes should cause any more lag than existed prior to the update.
Are you experiencing lag on all servers, or just Smogon University? Because the SU server lags sometimes due to the large number of users and battles going on. That has nothing to do with the client update. Log on one of the less-trafficked servers (like the CAP server, for example) and see if your client is still lagging. If the client does not lag on all servers, then it's likely not a client issue.
Even if your client does lag on all servers, there's not much we can do about it -- since it does not lag appreciably on any of the test clients we run. I've asked many, many users about performance of the client -- and all reports are pretty much the same. There is a small mainchat lag on SU, and almost none on other servers. That's perfectly consistent with traffic and server load. If you are experiencing slow performance, then it is probably something particular to your machine or software configuration.