I took delivery of the Plusnet supplied 585 v8 modem router a few months ago and I can only state that it's performance has been outstanding on my moderately long line (att 42dB).
I installed the Plusnet supplied firmware when I got it and can honestly say that it's been the best of a long list of routers I've bought. It maintains a connection for weeks at a time and the wireless connection has never dropped once. I get a constant download speed of 6.75 Mb/s on a ADSL2+ line. I'm just hoping that it never goes feet upwards as I'm sure I'd be hard pressed to replace it.