If you don't have any interest in color reading (magazines, comics, cookbooks, kids books) or tablet functions (movies, web, maps, PDA functions, games, apps), then you probably are better off with e-ink, even an older reader. Using the NC solely for reading text e-books is like buying a car that you only use to go to the end of the driveway and get the mail.
If you want a device for Android apps, putting CM7 on SD is a great way to go. SD will not necessarily perform any slower or worse than an installation on eMMC (the internal flash storage), but it is somewhat luck-of-the-draw how well it will perform. People have the best luck with 8GB or 16GB Sandisk cards, class 2, 4, or unclassed. Everything I used to get set up is at the link in my sig.
As far as the weight, it's counterintuitive, but I found putting a flip case with a picture-frame type stand on the NC made it much more comfortable to use. It actually adds weight, but between the stand and the cover flap, there's almost always a way to hold it that takes most or all of the weight off your hands. I went with this case:
http://www.javoedge.com/store/e-read...ble-nook-color
I also got 15% off by googling "javoedge nook coupon."