If your 6700 is getting a little long in the tooth (Face it, you know that it is), then here's good news for you. AKU3 is now available via a hack (completely unsupported and highly frowned-upon by Sprint and Verizon). So worth it, though, given the sheer number of bugfixes, tweaks, speed you'll garner from the upgrade.
Seriously, you deserve it after lugging that plastic beast around for so long. Give it try. Again, though, takes a touch of the technical skill, so not for the faint of heart.
Well-known Windows Mobile hacker Helmi (known for similar Windows Mobile hacking endeavors on the GSM platform) has managed to release Windows Mobile 5 AKU 3.3 for both the PPC-6700 and XV6700. In addition, both AKU 3.5 and Crossbow are expected to be leaked shortly for the device.
With the PPC-6700 still the most powerful device on Sprint and Verizon, owners can finally have a software installation that compliments their hardware's performance, even if Sprint, Verizon, and UTStarcom want to force users to upgrade via new hardware (that hasn't been released yet).