I have a PullRite SuperGlide that I'd recommend. It's much more expensive (~$2000 or more, it came with the Seville as part of the deal). I built a hoist in the barn to lift it out when I want to haul something. My mounts are under the bed so when I pull the posts, the bed is clear.
Sliding is automatic on turns so so you don't have to mess with releasing the hitch, pulling forward, then relatching. The only real hassle is that you have to have a catch plate that actuates the hitch to let it slide. I have no idea what would happen without the plate but I'd bet it would be interesting.
Al & Linda
2013 GMC Denali 3500HD SRW, Crew Cab, Std bed, 6.6L Duramax, Allisons, PullRite Superglide, Triglide
2011 Crossroads Seville VF35CK11