If you just need the YouTube-feed from a specific user, I wouldn't use the Youtube API...
You can simply get the feed from YouTube like this:
Code:
NSString *xmlString = [[NSString alloc] initWithContentsOfURL:[NSURL URLWithString:@"http://gdata.youtube.com/feeds/api/users/--USERNAME--/uploads"] encoding:NSUTF8StringEncoding error:nil];
NSLog(@"%@",xmlString);