TL;DR: Yes, very much.
I’ve written a number of blog posts on LastPass security issues already. The latest one so far looked into the way the LastPass data is encrypted before it is transmitted to the server. The thing is: when your password manager uploads all data to its server backend, you normally want to be very certain that the data visible to the server is useless both to attackers who manage to compromise the server and company employees running that server. Early last year I reported a number of issues that allowed subverting LastPass encryption with comparably little effort. The most severe issues have been addressed, so all should be good now?
Sadly, no. It is absolutely possible for a password manager to use a server for some functionality while not trusting it. However, LastPass has been designed in a way that makes taking this route very difficult. In particular, the decision to fall back to server-provided pages for parts of the LastPass browser extension functionality is highly problematic. For example, whenever you access Account Settings you leave the trusted browser extension and access a web interface presented to you by the LastPass server, something that the extension tries to hide from you. Some other extension functionality is implemented similarly.