UKC

The last mat I bought for camping must have been about 30 yrs ago, a very basic karimat. Now starting  up again and they seem to have advanced massively, I'm looking at reviews etc on goon tube and am aware now of the R value they are given, my question is:   is this all hype ? or will I actually notice the difference if I get a pad with an R value of 4.5 rather than say 2.  Thanks

I cannot give a definitive answer but I am sure I feel the difference when summer bivvying in the alps.

It depends if you plan on going camping in the summer months a lower rated r value mat would be absolutely fine and you may not feel the difference between this and one with a higher r value. Having winter camped  basic self inflating thermarest (trail lite r 3.2 approx) versus the thermarest xtherm (r 5.7) I have now I can tell you I have definitely noticed the difference in warmth and comfort. Of course the best performing mats are more expensive, and if you don’t need top performance in terms of insulation or pack size then a cheaper mat is absolutely fine. And any mat closed cell, self inflating or inflatable is better than no mat at all. 

I'm sure you'll find the modern mats way more comfortable than karrimats were 30 years ago. As for insulation - I feel the difference (but sleep cold anyway). You can always beef up the insulation by sticking a closed cell mat (like those original karrimats) underneath, but then you lose the advantage of the small size of modern mats.

And the winner is .. ... drum roll... ... ...

https://alpkit.com/products/numo?variant=40691728056425

I'd say yes. I bought a Exped downmat 7 after trying to save pennies, but being cold on the other mats, I finally bit the bullet and the difference was unbelievable. More comfortable too. 

Thanks for your replies, splashed out and gone for a Big Agnes, not the lightest buy reasonably so, and pretty compact, looking forward to trying it out