I've subscribed to Big Finish audios in the past, both on their main Dr Who range and on other series. They are hugely experienced and are more than capable of turning out top quality audio drama, as Erik says. I'd concur that you can't really compare an audio play with all the voice talent, music, sound effects etc and a recording of someone reading a book, which can easily take 8 or 9 hours. The price point is a little on the expensive side, but it's certainly in keeping with their product line overall.
Having said that... generally speaking, the most successful of Big Finish's audios are the two disc ones, an hour and a half to two hours. I find they often struggle to achieve the same level of storytelling on the one disc, one hour stories. In those instances though, it's usually a factor of what the source material demands. I'm currently listening to season 4 of their Jago and Litefoot series, and have found the previous three seasons - each consisting of four one hour stories - to be magnificent; tightly plotted, great acting and excellent direction and production. They have had many successful productions across a range of genres, so I'd be very hesitant to label them 'not fantasy fans.' So I'd also echo Erik, and urge folks to keep an open mind - they are more than capable of producing something of the highest quality. Whether they will or not, or whether other constraints will undermine it, remains to be seen. I'd love to know how this range came about though, who approached who, and what the decision not to produce it as a two disc range was based upon (I'm guessing cost and uncertainty about the saleability).
Oh, and all of their products are generally available for download as well as in physical form.