I do miss expandability and features. Nothing quite matches the look of nerd envy I got when I popped a folding bluetooth mouse out of my laptop's ExpressCard slot.
Sure. The original HP RJ316AA PCMCIA version was probably more comfortable, but I had the MoGo X54 ExpressCard model which was still pretty good. Both of them charged via the card slot. I wish laptops still came with an ExpressCard slot just for that mouse; I hated giving it up. Plenty of pictures and data on them if you Google the names.
With the way things are these days I'd settle for a mouse of similar flat dimensions and folding design that adhered magnetically to the lid of my laptop.
