I came across a brand new pair of Conti Speedkings (racesport 26x2.2), for not alot, so have put them on to replace the RaceKings(protection 26x2.2), for the summer months. Have to say that they feel pretty good on tarmac and gravel/dirt/ridgeway trails and the pair saved approx 400grams.
The SK may have less rolling resistance and be faster on tarmac but, as another said upthread, i found the RK to be very, very, good, on tarmac, and has tread that is more capable elsewhere, so i don't think the trade off is worth it, for the SK, at full rrp. The SK also goes from super quiet to an unnerving angry growl when you lean it over onto the little side knobs.
For cheaps, though, it is worth a shot to see what they are like compared to the RK as my routes aren't ever super muddy and i do alot of road miles between off road bits.
Edit to add for anyone interested in these tyres:
The first proper hard ride today on the SK's. Weather was good and everywhere dry as a bone. I pumped them up harder and that cured the angry growl, when cornering on tarmac, and way more stable as the carcass is more akin to butyl innertube than a tyre!
The off road section was a good number of miles of hardpack chalk/dirt, with a dirt/stones/grass covering, and i have to say i was very impressed, with the traction and grip. Honestly felt more confidence inspiring than the RK's, on this terrain, and encouraged some spirited riding!
The downside was the higher pressure, required for tarmac, rattled me quite a bit(fully rigid) whereas the RK can be run softer, which is comfy. Being a heavier tyre it doesnt flop about as much on tarmac while still offering good grip.
The SK definitely has its place and is a top drawer choice for hardpack/graded forestry tracks/salisbury plain/new forest/disused railways etc with long tarmac links. If i had a second wheelset i would probably pay full rrp. If on a budget then the RK is deffo the way to go to cover all bases and conditions well.