They're effing relentless. I'm not allergic to their anti-coagulant that causes the bumps and itching, so I never really know when I've been eaten alive unless I feel them biting me. Which is a two-edged sword because I would venture to guess that I'm not immune to EEE or West Nile.
Last night was brutal--it was unbearably humid and you have to wear long sleeves and a heavy enough fabric to prevent them from biting you right through it--which means you sweat like a claimer in a stakes race and wear off the repellant in 20 minutes. Sweating DEET into your eyes and mouth is a real treat, too
The non-DEET sprays are for crap IMO.