We were up there Thursday night – horizontal snow at Forest Chapel (bottom of Charity Lane) and yes, that bit was absolute sheet ice – lethal. The rest of the trails were lovely though – crunchy frost / very thin snow at worst.
For those that haven't been there for a fair while, there's a new-ish downhill in place (not the epic 'secret' hardcore downhill, but the one from the seats at the top of Nessits now has two options – the old sweeping one and a new one that starts ok, but pops out onto a motorway width track, sadly.)
The trails have settled down since the felling started earlier in the year and now that it's frozen is especially fast. Have fun, but go up the north side of the forest (on the concessionary bridleway) and down the south side – and don't forget Oven Lane from Forest Chapel as an extension to Charity Lane for downhill fun. I'm pretty sure the concessionary bridleways are shown on the latest 1:25k OS map. HTH.