Cleveland: D
If Dan Gilbert is paying attention, he should ask David Stern to void this trade for "basketball reasons."
First, let's follow the dead money. Walton makes $6.1 million next year with his trade kicker; Eyenga makes $1.1 million; neither or them are likely to play much or do anything of consequence if they do. So Cleveland swallows $5 million in dead 2012-13 salary.
For the privilege, they get a first-round pick from L.A. that will likely be in the 20s. The interesting part here is that when teams have done cash-for-late-first-rounder deals, they've typically valued the pick in the $3-4 million range. At best, the Cavs slightly overpaid on this part of the equation.
But wait, they also gave up a really good point guard! The Lakers essentially got Sessions for free; it was a fair deal just to give them a first-rounder to take Walton off their hands.
And there's more, although it's of lesser value. The Cavs also sent L.A. the right to swap first-round picks with Miami in 2013; the Cavs currently own the Heat's pick that year.
L.A. Lakers: A-
The only reason I put a "minus" here is my one misgiving about Sessions' fit into the Lakers' offense. He's a slashing, pick-and-roll point guard who needs the ball in his hands; spacing the floor for Kobe isn't really his thing. He'll likely be at his best when Bryant is off the floor, as the catalyst for the second unit.
With that said, Sessions is such a huge upgrade on the Lakers' current point guard mess it's not even funny, and it will likely take much of the strain off their three stars to play 40 minutes a game and take all the shots.
Defensively, he's kind of a sieve, and so he won't cure the vulnerability to quick point guards that has bedeviled the Lakers for years. But he's a good rebounder and, again, his ability to create off the dribble gives them a dimension that was badly lacking.
Sessions is also a free agent after the season, potentially; he has an opt-out in his contract. The nice thing about being the Lakers, however, is that nobody is a flight risk. If the Lakers want to keep him, they almost certainly can.