The bottom line is that this makes sense for a team that can afford the luxury tax. The Leafs, Lakers, Knicks, etc. would be doing this if they could. Heck the Nets tried and failed hard in the soft cap NBA. So I can see this as a net-positive for a team like the BoSox, even if they don't earn all their money back 'value' wise. They can afford to eat value if it means a front of the line player.
However, if you apply the same deal in a budget team's payroll, it looks ridiculous, borderline insane (Exhibit A: http://www.spotrac.com/mlb/miami-marlins/); and if you apply it to a mid-tier team like the Blue Jays, it looks like a poor use of valuable 'salary space'.
Therefore, I view this as one giant MEH. It makes sense for a team like Boston and in the grand scheme of things, shouldn't hinder them too much. This type of deal would be disaster for a team like the Jays or similar salary restricted team. So overall, meh. Just sucks it's in the AL East...