Everything I've read from people who switched to M8N report either better performance, or essentially the same performance, or within margin of error anyway. I hadn't seen any widespread problems. What "problems" could it cause? I do intend to keep the old GPS and cable in case it needs to go back to 3DR (again).
I totally agree that the M8N does tend to display more satellites than it can actually make functional use of. And people who fixate on number of satellites buy it based on that alone, which doesn't actually mean anything. So I'm not buying it to have a fancy sat count.
Some people get better acquisition time. Some stay around the same, or at least within a margin of error. I think the new RFI shield might make the acquisition time between the stock GPS and M8N remain more consistent and similar. At least that's my hope. If the M8N works better, super. If it works consistently well the same as the stock one, I'm happy with that too.
What sells me on the M8N is it's ability to KEEP a lock better than the stock GPS. When I walk up to the Solo and lean down to look at the GoPro, the GPS is lost. When it pick it up to carry it, the GPS is lost. That tells me it just barely has a descent lock and a bird flying by at the wrong time could kill it. Whereas people with the M8N report significant improvement when keeping a lock once it's acquired. Now, again perhaps the RFI shield will help with that too. But if the M8N is already better at that, the RFI shield can only help it be even better. That reliability means a lot to me.
Plus, it's something to tinker with. It's either that or watch 7 hours of Law and Order reruns.