I fished the Forebay for about 7 hours from my belly boat on Wednesday, May 2nd. It was overcast and windy most of the day -- perfect for browns, but only caught a couple. Here's a pix of a 15" rainbow I caught. Very dark coloration for a 'bow -- and fought more like a brown no leaps or long runs. Maybe he was lethargic due to the cold water or had the post-spawn blues.
I also caught a half-dozen lakers, most on a burnt-orange seal bugger, a Denny Rickards wooly bugger variant. Nothing huge, up to about 20" -- but lots of fun on a 5-weight. Most were caught at the inlet although there wasn't much water flowing in at the time.
I didn't see many fish on my finder, so it hadn't been stocked yet. I expect they'll get around to it within the next couple of weeks if they haven't already.
I only saw a couple of shore fishermen but it's early season and mid-week. I couldn't tell whether they were doing any good.
The water is cold so if you're tubing it, wear lots of layers under your waders.
All fish caught were released, so they're still there. Go get 'um.