I played through twice: With a fire-sorc (for Andy/Countess-runs-reasons obviously^^) lvl24 atm and a Barb lvl19
Just started a Amazon.
My short and unprofessional opinion? I just f**ing love it! There are all these little improvements, which in no way destroy the original feeling. It is still LOD. I love the new colourisation of the runes. Much easier to spot, although my keen D2 senses still hear the drops immediately 
The sound seems to have been improved. It sounds awesome, the ambience especially, The new rain in act one looks at last like rain and not like pixel-hail.
If you are a veteran, you almost instantly get into the old D2-feeling. I made runewords and knew what I have to to as if I never stopped playing.
I found some awesome lvl9-PVP Charms and hope that I cane relive the old lvl9-PVP-Days I hope they implement online soon for testing, so this glorious side of LOD can be tested as well.
In short, I am so lucky to have been picked for alpha to playtest. So far, the only major bug I have found is the occasional missing of my merc. He just vanishes from time to time when walking longer distances.
jus my 2 cents… believe me, It will be a glorious game