My experiences are essentially the same as yours. Everything you have described closely matches what I experience.
With Tablo and the Amazon cube, I am totally satisfied. Much the same with the Apple TV, and recently, with iOS devices.
Like you, I prefer Amazon, but my wife prefers, and really only wishes to use/learn Roku. I have been trying to keep the Roku/Tablo usage for her in the laundry, kitchen, office, and Treadmill (four of my seven locations in the house ) equipped with working Roku. Unfortunately, my personal experience with Tablo and Roku has been, at best some periods of stability over the last eight years, but totally crappy performance for many months when new releases of software occur until bugs are fixed.
The fast forward and rewind on Roku work like absolute crap . Even with the latest improvement, which came within the last week or two from Tablo, I still get nearly constant freezing. My wife just turns off the TV and says “there must be a better solution”.
I have never been a cable or satellite subscriber , and began doing OTA television recording in 1970 with a half inch Sony EI AJ video recorder. Before Tablo, I used SageTV for many years, ceveloped, owned and operated by two brothers in Chicago who took pride in their code and reliability.
In the 52 years I have been doing OTA television recording and playback, I have never owned any equipment that has been such a continuing source of aggravation and reliability issues. Thankfully Amazon and others have apps which are well written and very reliable, and the Tablo firmware Along with the player apps excluding the Roku have reached a mature level.
Next step for me is likely to bite the bullet and buy three more cubes, insist that my wife learn and use the Amazon remote, and donate the Roku boxes.
Believe it or not, I get no joy from posting all these complaints and comments, and the many hundreds of messages I have typed and submitted are mostly a waste of time.
I am keenly aware of alternative technologies and spent my prior 60 years in electronics and engineering as well as commercial broadcasting and ham radio. I am thrilled to see Tablo survive and thrive, but dearly wish that they could fix this basic navigation problem on the Roku,or at least acknowledge that they are working on the problem with the intention to ultimately fix it.