Impressed with 8800NL, question about SNR & DL speed

[hh007billion]

Hi,

Impressed with my 8800NL on my fibre line I bought one for my sister who is on DSL. I reduced her SNR ratio to 3 and she's getting no errors on her line but even though the data rates look better on the router interface (Attainable Rate Kbps) she isn't getting any better download/upload speeds compared to her BT HH yet. Does it take a while before there is a noticable improvement, or should the benefits be immediately apparent?

Thanks.