The symbol/intermec handhelds are expensive, terribly unreliable, slow, require a lot of maintenance and are terribly fiddly especially for people with gloves on (as you'd expect in the freezer department in Morrisons). As for the software development side of things, you're pretty much limited to a subset of win32 that isn't very pleasant to use or a mobile CLR which is so incredibly slow it makes you want to hang yourselves. Then there's the incredible deathly pain of deploying the code to all those devices.
It took us three years to deliver a point of delivery system with the same staffing level with much smaller scope which was simply signing for stuff and listing a delivery schedule. The integration was done by a third party - we just passed messages back and forth.
They did a damn good job at TW on this one if you ask me.