I think the respec is a good thing. The lack of respec in D2 was a pain after you got to high levels and miss clicked or were wondering what that other spec would be like because you had to re-level another of the same class just to find out!
I think a good solution would be (based on what D2 was like):
Open/unranked: unlimited respec/no penalty. This lets the ultimate casual have as much as they like without being locked into a spec permanently. Also serves as a good place to experiment with different specs.
Ladders/Rank/BattleNet: Don't know how blizzard is going to do the online thing just assuming they do it something like they did before...
Make it a limited number of respecs 1-2, and have some cost associated with it. And for the Ladder characters, a limit of one or no respec option(s) at all. That would provide the more hardcore players with what they desire.
In the end, everyone wins...and you can always have a test character that has unlimited respec options to fine tune that build before you take it somewhere that it actually counts