Happy to hear the info here has been helpful.
Most of the tricks people have discovered for this and other WM phones involve regdits. Don't be shy - get a good WM6.5 compatible backup program, get a registry editor (resco or total commander are a couple of options depending on your price elasticity), and have some fun.
You can run the mortscript fixes I've posted without needing to do registry edits yourself, since Mortscript is capable of writing to the registry on its own.
Firmware updates are at the discretion of the mfr and carrier. Since Samsung hasn't seen fit to even provide us with a bugfix in 5 months, I doubt they're planning any additional dev time on the Intrepid (I'd love to be surprised, tho...really). 6.5.3 would be a huge improvement over the ancient build we've got.
Can't speak to the loss of data connection since I'm pretty much always in EV coverage, but unfortunately you're a classic case of Spring doling out replacement phones (hardware) for a software or network issue. All you're getting is often previously-replaced/refurbished phones that will have the same behavior. If you've never experienced this issue before I would be quick to point to the Intrepid as the source of the problem (specifically the build of WM on the phone or Samsung's implementation of it on this particular hardware). You can get any many replacements from Sprint as you want and they'll just keep giving you other people's returned hardware.
When I buy a phone new in the box, the only time I will accept a replacement for it is when there is very clearly a hardware failure, or a software failure so devastating that the phone cannot be recovered with a hard reset. Unless they bring out a new box and hand me the phone with the plastic wrap still on it, which is pretty rare...
Last point - WRT reg edits - every time you hard reset you'll have to redo them anyway, so it's best to just create a .reg file with your favorites. I've had to hard reset my Intrepid probably 10 times since I got it, mostly because I've been experimenting with things in order to get this thread filled with some (hopefully) useful things. But even so, eventually you're going to install something that bricks your phone and you'll have to start over. Maybe I'll post my .reg file if I have time later on, that may be helpful and something others can improve upon.