When I get home the bag liner always stinks. I wash it. My bag doesnt stink.
On the warmth front, theres no right or wrong answer, it depends.
If you dont get dressed to go to sleep then a liner will make a differnce, trapping air to the skin a bit differently.
When its hot, or you get a new neoair thermarest, you can sleep in the liner and rip the bag open to use as a quilt.
But $75 for a liner

Buy a 'reeely is' silk liner off ebay for ten bucks or sew an old sheet together.
If I was cold I would dress for it, and if that wasnt enough then bivy. Jeez it would have to be cold though.
I would never use a bag without a liner though, and it costs what ... 142 grams.
Every four seconds, somewhere in the world, an Harlequin Mills and Boon is sold ... Wot ...