The thing I would caution any one hiking in the high peaks of the north east from mid-April to memorial day weekend is mud. Not so much that it's like , "ew, mud! I don't wannna get yucky", but that the trails are especially fragile and susceptible to erosion this time of year. In Vermont, the Green Mountain club goes so far as closing the trails above 3000' for this time period on Camel's Hump and Mansfield. What I find is there is generally spring conditions down low, and snow up high. Somewhere in between, for about 500-1000' vertical feet or 0.5-1 mile, there is melting snow and deep mud. This band moves up the mountain from mid April to late May, location and size depends on many factors. I have read that accelerated trail erosion is due to the combo of heavy foot traffic, excess mud, and frozen ground under shallow thawed ground. Obviously, if we said we will never hike in the mud, no one would ever hike in the Adirondacks. Not climbing the big peaks is more voluntary in the ADKs. I would recommend seeking a ridge climb instead of a ravine trail, ridges tend to drain better. I would avoid perpetually muddy and heavily traveled areas like Colden, Algonquin, Marcy. I like the Pharoah Lake wilderness region or Lake George (tongue range) that time of year. Also a pretty well drained ridge in NH is the airline trail to Mt Adams or Madison. Valley Way (despite being a ravine trail) is usually in pretty good shape too any time of the year because it gets so much maintenance. I generally do not have any bug issues until June (about when the Green Mountain Club says its OK to hike up high, the bugs come out). If you do go, just be conscious of trail erosion and try to stay on the rocks as much as possible.
http://www.adk.org/trails/High_Peaks_Hi ... Mud_Season
(interesting the adk link talks about May though mid-June as mud season, it really depends on the year though, many factors like was it a big snow year? Is it a warm/cold spring ? is it a dry/rainy spring? etc... I would guess in late April the snow pack will be mostly melted away in the lower elevations, like Avalanche lake, but the lakes them selves I think will still be frozen over)