I have watched various "seasoned masters" do aikido and would say that none of them would be able to win a UFC tournament using aikido.
Firstly, all these UFC fighters are professionals. They fight for money which means they are trained by the best. They are young, in top condition and usually come from a strong background in boxing, kickboxing and wrestling. These guys aren't just anyone.
Secondly, the style of fighting in these tournaments is very refined. Aikido uses intricate locks and throws that are very difficult to apply to someone who is not wearing a gi, strong, very quick and is wet with sweat.
Aikido is still a good form of self defence. In some ways its more effective than kickboxing or grappling. Have you ever seen the BJJ self defence videos? You would be suprised to see a lot of aikido techniques used against knives and grabs.
I have trained with many security personel, who come from a kickboxing/karate/kung fu background and are very suspicious of aikido. After a few lessons they think its the best thing for their jobs.