I have both units. I have them on right now (1st floor middle room, 3 floor house). The HCx is giving me 22 ft accuracy. The original won't lock at all. In fact the original won't lock as I walk toward the window unless I press it against the glass..
The sensitivity is so much improved that it can not be under estimated. Also, the ability to load so many maps is awesome! No need to reload for every weekend trip.
As for the rubber pulling away from the unit. Let me tell you that it is a design nightmare and will likely happen with any small plastic unit with an adheared rubber shell. Especially one that tends to get tossed around and carried in backpacks, pockets, etc. Believe it or not those are quite abusive environments for such a small unit.
What makes the adhesive delamination issue even worse is the extreme temperature ranges. To hot and the adhesive softens above its glass transition temperature, too cold and it will become brittle, coupled with the differences in the coefficients of thermal expansion between plastic and rubber and you've seen the results.....
I guess what I'm trying to say is that it sounds like you've gotten alot of use out of your unit and it's showing signs of age and maybe not design flaws.
Mike
P.S. I own an adhesive development company. We design materials for NASA, etc..