I thought Mike reported a 30% gain in a post somewhere in this thread.
Dish gets roughly 30mbit/sec on the SD QPSK transponders and roughly 41-42 on the 8PSK ones. So, it is about 1/3 more bits. Of course, that would only be seen on the SD TPs used for national channels, SD locals on spots are not going to buy any national channels:
On 119 that would be (according to "the list") TPs: 6, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, & 22 or 16 Transponders
On 110 that would be TPs: 1, 2, 3, 5, 6, 7, 8, 9, 10, 11, 14, 15, 16, 21, & 24 or 15 Transponders
On 129 that would be TPs 21
So essentially around 32 transponders converted, assuming 10mbit each 320 megabits/sec increase. If they do 5mbit/HD channel, enough room for 64 channels, 4mbit 80 channels. But, you have to have matching EA bandwidth available too. Perusing 61.5 and 72.7 it looks like they probably have 5 TPs worth free, which would be around 200 mbits actually free. So, more likely 40-50 HD channels of bandwidth, or maybe 10-15 4k TV channels depending on how Dish wants to spend their bit budget.
Remember EA is essentially 64 (well 2 TPs could go away since they are officially unassigned) transponders, 32 on 61.5 and 32 on 72.7. Yes they use some on 77, but it is not really primary. On WA they have 82 TPs, far more capacity.
** Usual disclaimer these numbers just come from a quick perusal of "the list" and Dish network could have completely different plans for any possible bit budget increases seen with an 8psk conversion.