Based on my results last night I think we can explain what you're seeing.
Basically, as detailed in the other thread I padded down the signal from my amplified antenna by 5dB and things got very much better, in fact almost all of the "Loading please wait" issues went away - except when operating a microwave oven in an adjacent room.
With RetiredEngineer's help we came to the following conclusions:
1.) The video decoder in the Roku is very temperamental and really wants to see a pretty pristine stream to perform well.
2.) In my setup, the excess signal at the OTA interface was causing the transcoder to either drop packets or to operated with weird timing. In either case it was creating a video stream that was anomalous enough that the Roku decoder was having problems. Apparently the behavior of that decoder is to back up and try again when it encounters difficulties.
3.) Once the really bad OTA issues were resolved, it exposed the fact that I was getting packet drops over the Wifi interface that were creating similar difficulties. A microwave oven, being in the same 2.4GHz band is a pretty decent interference source, and if your SNR is low on that interface it is liable to cause dropped packets.
Clearly the excess signal on the OTA interface is somewhat unique to my system, however if you are running a distribution amp you might see that as well. Of course, anyone running the Roku over Wifi is liable to see dropped packets there.
I would suggest that you go into the secret WiFi menu in the Roku and look at your SNR. The key sequence to get to that menu is >Home< (5 times), >FF<, >PLAY<, >REWIND<, >PLAY<, >FF< (that's from memory, google it if that doesn't work).
In my setup my WiFi SNR was in the 10~12 dB range, which is apparently too low. By repositioning my WiFi router and antennas I got that up to about 18dB and I'm not seeing any issues. More SNR would probably be better and wired ethernet the best.
My guess is that the Tablo developers were testing with some fairly good OTA and WiFi signals and they just never saw these issues. If I were them I'd buy myself a click attenuator and put it between my antenna and the Tablo and see what happens as I step the signal up and down. Also, making sure that the WiFi network I'm testing against was something like real world would probably be a good idea. In a lot of test labs you see people testing against a wifi network where the router and nodes are all on one bench, which isn't worst case to say the least.
The Roku video decoder seems fragile beyond what is good for a robust product. I don't know if Tablo wrote a decoder that is part of their app or if the decoder is a service (API) provided by Roku, but it seems it could be improved.