I don't want to speak out of place, so I will limit my response re:Uniden to say that UPMan is looking into it as time allows within his busy schedule.
Now onto my observations.
Basically it is substantially slower on large numbers of active (quick key enabled) GPS "sites" (I use the term site, but I mean anything that has a GPS location that needs to be unlocked so this includes groups now).
I did a very brief test of the 996XT and 996T and found that the 996T had times of 14 seconds and 27 seconds to lock/unlock when entering or leaving a defined area. The 996XT had times of 20 seconds and 61 seconds.
The problem with this was that the 996XT only had about 100 GPS "sites" to process, the 996T had over 200.
I later did a one off test of the 996XT with probably 200+ sites to be processed and it took over 2 minutes to unlock a defined area.
I realize these tests are anecdotal, I don't have the time or the patience to engineer and then execute a test that is statistically significant. Suffice it to say that the 996XT is slower in locking/unlocking systems based on location
It is clearly slower. My main concern is for when I am traveling on the interstate or other highway on trips and have defined a town with a ~1 to 1.5 mile radius and that I am half-way through the town before it unlocks. Heck, if I have too many systems enabled (quick key on) I could be through some towns before anything even happens.
So the work-around is to spread systems out across quick keys and to keep to a minimum the number of GPS "sites" the 996XT has to process at any one time.
So where I used to keep the whole Colorado DTRS enabled using one quick key (that is 186 sites that I had in 8 systems) on the 996T I now have it divided across six (6) quick keys that I will enable/disable based on where I am traveling.
For my home area in the DFW metroplex I have done basically the same thing of dividing up systems more evenly across quick keys.
I am personally rather frustrated by this. The reason the 996XT was so great for me was that with the 25,000 channels (I had run out of space on the 996T's 6,000 channels) I was going to be able to keep it programmed with ALL my stuff for trips to various areas (Illinois, Missouri, all over Texas, New Mexico, Colorado, Oklahoma) without having to reprogram it do each trip like I would with the 996T.
I personally hope that the P25 performance is substantially better then 996T to make the 996XT worthwhile.