I'm not a fan of Barkley as a top 10-20 pick and a starter day one, but as a mid 2nd round pick that can have time to groom and improve his arm, I really like him. He has great skills and the right attitude unlike the other USC QBs. Big Ben may only be 31 but the way he plays he's bound to get injured again, and how about having a real backup QB, not the collection of Batch, Leftwich, and Dixon.
Best Case #1
-Big Ben injured for 3-4 games. Barkley comes in, looks great, and turns your 8-8 season into a 10-6 playoff season. Then in the offseason he is traded for a bounty like Schaub and Kolb.
Best Case #2
--Big Ben injured, Barkley looks great, you have your QB of the future and trade Big Ben for a ransom.
Worst Case #1
-He sucks. A mid-2nd round pick turned bust, not a big deal.
Worst Case #2
-Big Ben is healthy 64 straight games. Barkley never sees the field and is traded for a 3rd/4th or becomes a FA.
Now, #48 is probably too early for a Mallett type pick, but I think it's a worthy investment.