I'm very happy with this developer and use it at a dilution of 1:9 at a temperature of about 25*C for no more then 2 min. This gives me a gentle warmth I like.
When I need a cooler print colour I mix in a little of their Cooltone developer (sadly no longer made, but fortunately I have a few litres). For example I will mix, 80ml of WT + 10/20ml CT to every litre of working strength solution. This gives me a very subtle duo 'tone' look to the print.