host header load-balancing

So what it sounds like you need is to balance based on URI first, and then User-Agent after that. I.E. if the user is accessing msie.foo.com/login, then decide where to route things based on their User-Agent. Otherwise, send everything to the default pool, since it is the one that is set up to handle all of foo.com. Does that sound correct?

If so, you're awfully close, and just need to add another conditional. Try this:

when HTTP_REQUEST { 
  switch -glob [HTTP::header value "User-Agent"] { 
    "_MSIE 6_" - 
    "_MSIE 7" - 
    "_MSIE 8" { 
      if {[HTTP::uri] eq "/login"} { 
        pool site-10.130.14.98_9610 
      } else { 
        pool site-10.130.14.98_29710 
      } 
    } 
    default { 
      pool site-10.130.14.98_29710 
    } 
  }
}