Any thoughts on these rims? They will obviously be good in the soft stuff, but will they be strong enough for everyday summer use when things firm up? Will the extra width have a negative effect when you are not in snow etc. is there too much footprint for summer riding?

strong enough – why not, plenty heavy, folk ride them in all seasons with 4″ tyres AFAIK.

At 80mm wide though even a 3″ tyre will not be as wide as the rim and depending on the riding you do the rim may be vulnerable to damage.

Surly Rolling Darryls

Daryll by Moose.2008, on Flickr

Any 80mm rim will give a nice profile to a Larry.
I switched from a 65 lM to an 80 GFS and noticed how much more stable the tyre felt at low pressure.

As for if they’ll be strong enough. I drilled some BFO holes in my 80’s and they’ve not died yet and from what’s been said so far about the Darrylls they’re a better quality rim.

Oh and they don’t look like that picture up there^^^
They’ve got one row of holes not two

OP you oughta join the mtbr fat bike forum