Sensible move and the whole mainframe aspect will apeal to lots, some as/400 love or whatever they clal it thesedays and ther will be alot of happy people out there, well except your local salesperson. Who in the past could sell a new bit of kit every 5 years or so will now sell a cloud package and poof, he is forefilling his own redundancy plan. Also for the companys that over the years made money hosting mainframes and the like for companies and in all effect offered cloud based services over leased lines will probably be more impacted if they havn't moved on already and those that have will have already proved to the customer that they can use such a system and open them right up to IBM's hands who will be able to cut the better margin breaks.
Also lets IBM get some extra millage out of some older kit, which whilst not end of life is not exactly the prime pick.
Now if they offer up usage for training for individuals with come cheap certification, well, they could make alot of people happy. Can't see how it can fail as they have all the locations and network etc etc in place to do this type of service, so be interesting.