Question : Problem: Is WPA pre-share key encryption secure enough for wireless in production?

Q#1 If the WPA encryption is used between AP and wireless client, how secure is such encryption nowaday?
Q#2 What factors determine the secureness of WPA encryption?
Q#3. How long does it take to 'hack' WPA encryption?

Thanks.

Answer : Problem: Is WPA pre-share key encryption secure enough for wireless in production?

WPA encryption (TKIP) is fairly secure.  Researchers have recently been able to half-crack TKIP, but it's not something that is widely done yet.  If your devices support WPA2 it would be a more secure option as it uses AES/CCMP encryption.

As far as "secureness" they are pretty close, but work a bit differently.  With the WPA2 specification it was decided to switch to AES since it was the encryption standard of NIST.  

Both are more secure than WEP by far - it has been cracked in under a minute.