There will be numerous midnight launch events in all over the world. I'm guessing their length and greatness depends on the size of each store and each city , but it will still be fun to attend.
Blizzard announced a list of retailers who will host the events, and I was suprised to see there was one in almost every city in most countries.
Here you can find a list of the events in every country :
http://media.wow-europe.com/diablo3/launch-events/en/index.html
Here's the Greek list for example :
Athens
Console Club Opening Time: 20:30, 37B Irakleiou Ave. 141 22
Games Explorer Opening Time: 20:30, 31, Panormou St. 115 22
Multirama - Peristeri Opening Time: 21:00, Peristeri - Ethnikis Antistaseos 38-40
Public - Ag. Dimitrios Opening Time: 21:00, Vouliagmenis Av. 276
Public - Glyfada Opening Time: 21:00, Karagiorga 4 & Lazaraki
Public - Peiraeus Opening Time: 21:00, Grigoriou Lampraki 152 -154
Public - Syntagma Opening Time: 20:30, 1, Karageorgi Servias, Syntagma Sq. 105 63
Public - Syntagma Opening Time: 21:00, Karageorgi Servias 1
Public - The Mall Athens Opening Time: 20:30, 35, Andrea Papandreou, Marousi 151 22
Public - The Mall Athens Opening Time: 21:00, Andrea Papandreou 35 - The Mall Athens
Ioannina
Public - Ioannina Opening Time: 21:00, Pirsinella 4 & Melanidi
Irakleio
Multirama - Irakleio Opening Time: 21:00, L.Dimokratias 25 & Geronimaki 1
Kalamata
Multirama - Kalamata Opening Time: 21:00, Aristomenous & Kritis
Patra
Multirama - Patra Opening Time: 21:00, Ag.Andreou & Votsi
Salonica
Public - Pylaia Opening Time: 21:00, Mediterranean Cosmos
Thessaloniki
Public - Tsimiski Opening Time: 20:30,24, Tsimiski & 31, Mitropoleos 546 24
Volos
Public - Volos Opening Time: 21:00, Ogl 28 & Kontaratou 9
Where will you go, if you go?