Up until this last year or so, the SF340's have noticeably provided the most reliable service the islands have seen. However nowadays, there is not a day goes by without a couple of "technical" delays. There has been lots of management changes, perhaps therein lies the problem.
The Sumburgh-Aberdeen is Loganair's bread and butter route with 5 or 6 flights perday, and perhaps a larger aircraft would be worthwhile. The high-wing aircraft do not quite have the cross-wind capabilities of the old budgies and the Saab however.