I don't really get the complaints on the new UI. It was long overdue and in general it works much better and is visually easier to quickly get to channels if you have a lot of channels.
I agree that it's a much better-looking interface. However, I only have it on my Roku 3. The LT hasn't received the update yet, so I don't know how well it'll work there. I would be surprised if it didn't perform well (read: as designed).
My only problem so far is the Roku 3 occasionally freezes and has to be manually rebooted and the remote doesn't always interact instantly. My understanding is they are working on some bugs. I can live with that for now.
I've heard reports like this, but haven't experienced any problems at all with the Roku 3. Of course, others complain about Hulu Plus, but I haven't had a problem with Hulu Plus on any Roku in well over a year.
Haven't had any remote issues other than when the batteries were weak after extensive headphone usage.
Maybe Roku just likes me.
The search across channels is fabulous.
It works quite well. I never used the search feature much previously, so I can't say it's an improvement. I do most of my watching in the living room (Roku 3), so that's where the searching is. The Roku LT is in the bedroom, and rarely use it there. Maybe I ought to try the 4.x software search and see just how big of an improvement the search is.