A couple of weeks ago, on a whim, I bought a pair of Ultimax Silver Crew socks at an outrageous £16 something. I've tried them out, on The Beacons a week last Friday and, to test the claims about antimicrobial odour control, I have since used them every day, without washing them, for the last week on dog walks and one 8K walk on the Rhymney Valley Ridgeway.
They certainly remained odour free but their comfort and warmth are beaten hands down by any of my Bridgedale socks. These socks are colder, what is more, the top band is far too constrictive and my ankles could never be described as "stout".
I normally change my socks, or at least my liner socks, every day when I'm on the hill for more than a day or two anyway and the blurb doesn't say whether silver has any effect on the build up of fungal spores.
I don't think I shall be buying any more of these and those I already have will be reserved for summer 1 day walks.

I'll second Bridgedale socks - most of mine now look like crap but are still very comfortable - I've got the ones which are fleecy on the inside and are labelled 'coolmax' (as are many others confusingly)

Coolmax is the name of a wicking synthetic material and appears in many Bridgedale socks, hence the confusion. Ultimax uses Coolmax in some socks too.

I have some Ultimax Rugged Outdoor socks that are warm and comfortable and have lasted pretty well - I've had them over 3 years. However being a mix of synthetics they go stiff if worn for more than a day or two without washing. Bridgedale socks with merino wool can be worn for longer. I've found the Bridgedale Ascents with 30% merino hard wearing and warm. However nothing beats 70%+ merino wool socks like Smartwool in my experience. I can wear Smartwool socks for 2 weeks and they will still be comfortable.

Ultimax aren't brilliant. Like Chris says, the blend of fibres isn't ideal and I only ever bought one pair - at a discount, thankfully.

I don't rate Bridgedale either. I've only tried their normal 'hiker' socks but I find then not densely-woven enough.

My all-round faves are Smartwool - normal hiker socks for winter - all very dense and cushioned - and 'adrenaline' for summer.

I'm beginning to become a bit of a Smartwool addict as well, although Bridgedales were my favourite for a long time.

Last Xmas I was given a pair of Tesco's hiking socks, £5 for two pairs. They are great! For the money I don't think you can beat them,. I wouldn't use them on multi-day treks, but for short day walks they are superb, IMHO. Means you can save your "good" socks for something more adventurous ;)