Waterfield - all the way (although pricey)Sleevecase only @ sfbags.com
, I got these and they are simply sweet & high quality (i.e. not cheap). I'd recommend getting the horizontal flap along w/ should strap & piggyback (esp. if you forego a bag for the entire sleevecase). I also got the Cargo bag combo & would positively recommend to anyone (chk out the site's testimonials).
On the affordable end (not a sleevecase but happy customers who have Dell's i700m) JanSport Modus Small Messenger in Anarchy Green (not the pink one)
. Can end up being very cost effective w/ all the ebag 20-30% coupons flying around. g/l in your purchase.