Here are Hamilton's OPS during the past 5 seasons:
2009: .741 (89 games)
2010: 1.044 (133 games) (MVP)
2011: .882 (121 games)
2012: .930 (148 games)
His production is really impressive, but is he really a $30m player with those numbers?
OBP:
2009: .315
2010: .411
2011: .346
2012: .354
He's not a guy who, if his power disappears, is going to make up for it with great ABs.
Finally, if there's a chance that he's been juicing/HGH'ing, I would be afraid of a post-contract letdown.
If the Sox sign him I will be excited like most other people, but it doesn't seem like he's a sure-bet to be better than, say, Adrian Gonzalez was yet he would cost 10m more per-season.