I have a Patrick Eggle New York and apart from my nylon string classical, it's by far the lightest guitar I've played. Wow, sounds and plays good too.
Like I mentioned earlier, the guitar I use most by a long way is the Godin Solidac. This guitar is so versatile and can sound like nearly anything, including a great immitation acoustic sound.
It does weigh a ton and yes, I get back ache sometimes. Thing is to move around, try different strap lengths and a good wide strap should help quite a bit. I can put up with some back ache as long as the guitar sounds and plays well. I don't even notice usually to the morning after..
Take care, Gordon.