Did the Gen 5 upgrade solve your Windows update problem? I am having the same type problem and was thinking about upgrading.
So far it seems to be better, but it hasn't really been long enough and I haven't done enough updates since the Gen5 upgrade to say for sure. Even sometimes with Gen4 they went well, though more often than not they were slow for the last six months or so. Between my three computers I've done five or six updates since the Gen5 upgrade and they've all gone very well. With that said, they were all updated at least a day or two after the day the updates were released, so the Microsoft servers probably weren't as busy at that time, and I think how busy their servers are could be related to the problem, with them basically being more touchy to the latency of satellite internet when they are busier than when they are not. That's just a theory, but it seems to fit.
I can say, though, that even if it ends up that the upgrade to Gen5 didn't help much in the update area, I will still be glad I did it, just for the higher speed and generally lower price for the amount of data I get. Plus, if I ever go into FAP (I have yet to with Gen4 or Gen5), the higher FAP speed will surely be appreciated. I like the built in Wi-Fi, too, though I didn't think I would.