Aquiss should definitely be making the "new customers" aspect clearer as it's a key limitation of the promotion and must be made clear on the offer itself. As it is a casual surfer wouldn't have even noticed the small print on their site as it wasn't mentioned on the big banner.
As for the speed "dropping" to 19Mbps, that's actually a requirement of the ASA upon all ISPs and you'll note that most big providers have now adjusted to promote more realistic performance. It doesn't mean the ISP is any slower than it was yesterday.
Mark 'Winter' Jackson
Editor-in-Chief - ISPreview.co.uk