I cannot judge "decline" because I dont know what it used to be like. But I can definitely echo the above sentiments about AW searches coming up with only a handful of pages, from which I could count the number of genuinely tempting profiles on my fingers, and from which I could count the SPs who have actually bothered answering an enquiry on my thumbs. Given that they were both hotel based and I am not too keen on that (see the current "rumbled by reception!" thread in the UK forum), I haven't even been motivated to buy a phone yet! Parlours have sufficed to scratch the itch without the hassle, commitment and potential B&S of AW bookings. On that topic mind you I lurked on some parlour websites and twitters for some months before I mustered the courage to actually visit - it seems some have gone from advertising a seemingly large and often-changing rota to listing a smaller cast of 'stalwarts' plus regular appeals for new staff. So perhaps that is some "decline" there too.
And judging from the reviews forum you would think Swindon is the biggest city in the region!
Still, as zak observes, it may be for the best, financially speaking - I've blown my holiday budget for the year already as it is!