Re: techniquies in street fights
Another importance of shomen uchi is that the elbow is low - often making it difficult to do such techniques as ikkyo, if the cut has been completed. Thus it is useful to practise this attack (many wuchi people would do vertical punches and also keep the elbows low).
I think aikido is good at dealing with sudden lunging type attacks or any type of grabs - although it has applications in sparring, I think it can be difficult to use in sparring. It is useful to learn how to strike as well, so that, if people hold back too much in their attacks, you can strike (even you need to?!)