Thanks for interests in ohphoneX. We just released 0.1a that fixed several bugs and has better audio/video quality.
As to the Nikotel VoIP, I beleve they are using SIP, not H.323. We do plan to start a SIP phone application soon, or a H.323-to-SIP gateway so you can use ohphoneX to talk with SIP clients such as MSN Messenger.