I can't sat about them directly, but many of the sell-and-install companies use subcontracted installers who get paid peanuts and even if the product is good, the installs can be lousy. With windows, proper installation is crucial to getting the advertised thermal performance so you should see if they have a webpage detailing how it is supposed to be done, then be there and make sure the installers do it that way.
What worries me more is your mention of termites. If they are into the windows the odds are that you've got much bigger problems that need to be addressed before the windows. Not much point putting windows in if the walls aren't sound leaving them to fall out next year!