i have no lid on our tanks. IMO now that i have gong topless i dont think i would ever use a glass lid again. You get better gas exchange, better light, more evap so cooler tank.
all possitives. the only neg i can see are more top off but with a 10 gallon thats no big deal. and if you have a fish that tends to be skitich you may want to get some egg grate from your local hardware store just to prtect the fish from the light if they jump