Nice shot. Check your focus of the fore ground, try and keep lights out of the fore ground and I suggest using a higher f stop. I managed to capture some lightning last night - let me know what you think - there are two photos of mine in the General Gallery.
They're brilliant! I was trying to keep the lights out of the foreground for a while but couldn't find a way to get it right, there's only one window in my office so I was very limited on composition. Hopefully I'll be in a field tomorrow, during the day and away from the city so my comp should be a lot better (note the 'hopefully'). What effect does the f stop have on the lightening?