Blizzard has a Starter Edition for Diablo 3. You're limited to 3 Class, level cap to 13, no season or hardcore access, and Act I story mode.
 
I played for 2 hours and reached my cap, and played 3 more hours to get rare items to look like a pro ;)
I'm waiting for good sales for the Standalone + Expansion (I want access to the Crusader).
Now that you announced Diablo I porting, I'm getting tempted at buying :)