I use DEET, too. I've tried some of the others and even the Picaridin doesn't work for me. I live in an area that is full of deer ticks and 2 people in my neighborhood have progressive Lyme Disease; i.e. they got bitten back in the day and never got treatment until it was too late. One was an MIT prof who pretty much lost a lot of his cognitive ability. I'll take my chances.
I avoid the local trails at this time of the year, except for one that is wide and the foliage doesn't touch you. I got a tick bite last year. My DH found a tick, engorged, on my back, 2-3 days after I had hiked with a client. He got it off, but I did go to the doctor, who put me on a 3 day course of antibiotics. I generally don't go out riding when mosquitos are around, but they do spray here. When I was up in NH last weekend, there were lots of black flies at one point in the ride, which had me wishing I had put some repellent on. I did use it on a hike the next day, and it was a good thing. There were tons of mosquitos, flies, and various other nasty flying things.