I've got three comments on the Lakers' free-agency pickup of Houston's Ron Artest and the Lakers' decision to let Trevor Ariza depart via the same path:
1. Artest is, without question, a better "player" now than Ariza and Ariza isn't likely to ever reach Artest's stature as a "complete" player (Artest handles and passes better; he's much more 'physical'; and he is a superior rebounder and defender).
There is no doubt that in terms of "sheer talent", the Lakers are better off after the "swap".
2. I have a gut feeling that Ariza was made to look like a better player than he actually is while playing for the Lakers. The triangle offense, especially when it possesses components the likes of Michael Jordan and Scotty Pippen or, in the case of the Lakers, Kobe Bryant, Pau Gasol and Lamar Odom, makes the "support" players much more effective/impressive than they would in other settings.
Will Ariza be as impressive with the Houston Rockets as he was with the Lakers (and wasn't at his first two NBA stops in New York and Orlandoi)? Probably not.
3. Even after explaining my stances on 1 and 2, I'm not sure the Lakers are going to be "better" off in either the short or long terms.
Ariza fit in perfectly in his role with the Lakers. He was the ideal "third, fourth or sometimes fifth option", was a good (if a bit overrated in that regarded by much of the L.A. media) defender and always played with "energy".
Will we be able to say the same things about Artest next season? Will his ego allow to be a near afterthought at times, offensively, when he is on the floor with Bryant, Gasol, Odom (assumes he is re-signed) and/or Andrew Bynum?
Can he keep his temper in check?
It was definitely a role of the player personnel dice by GM Mitch Kupchak and whoever else was involved in that decision making.
But Kupchak & Co. have made a lot of outstanding decisions -- which led to the run the the title -- and they certainly are worthy of every benefit of doubt this time around.

Frank,
Agree with your assessment. I loved Trevor for his playoff run, but his overall year was not enough to warrant more than $5.9M a year, and in Houston he is going into a bad situation getting worse - no Yao - forget it, Ariza will miss the day when he could have told his agent to work it out with Mitch. The downside for the Lakers is two-fold - does this signing impact them signing Lamar and the eventual blow-up by Ron-Ron at some point.
The other dimension to this deal is the loss of Ariza as a defender. Trevor was an ideal defender to match up against opposing stars like Rashard Lewis. Now the Lakers have a bit of a height drop-off from their post players (Gasol & Bynum) to their wings (Bryant, Artest) & PG. If Artest slows down a step during his upcoming three years with the Lakers, Ariza's athleticism will be even more sorely missed.