Dreamwever live view very slow and laggy

Short answer: Switch to Design view (Ctrl + Shift + F11).

Are you working within a defined  local site folder? 

Does the site folder reside on your primary hard drive?

Lag in Live View can be caused by errors in your code. Cleaning any errors up may be all it takes to bring DW back in line with expectations.

Visit http://validator.w3.org/nu to get a listing.

Other items like external script references or using the @1552174 rule in your css have also been known to slow DW down. 

Is the testing server on your local machine with that power or somewhere else online? The live view uses the testing server to render your site in live view so network connections/firewalls/etc can all impact the rendering speed.  To be honest, I have not found live view to be buggy, but it can be slow at times so I typically just work in code view and preview in browser.