Yes, it is more limited than your tablet of phone (as to be expected), but not too much more than any other Smart TV suite out there. Would I like more apps, sure, but that is also up to the app makers themselves to support it as well. They added Playstation Now and Playstation Video as well as their Ultra 4K service last fall, so hoping Vue drops at the same time they drop it to other Android hardware. But for all the basic ones on there from Netflix to YouTube, etc., everything performs and looks remarkable. Those 4K 60fps videos on YouTube are mesmerizing. They look better than real life, lol.
I have not noticed any sluggishness, but then again, not being 'super snappy' may bother some, it is a hair 'softer' in response than the PS4 interface, so it does not seem to bother me. Also you can pin apps to your launcher, and organize them in different orders/types, so maybe people have not gone into the settings to make sure they are pinning it to where they want? I have not downloaded any apps yet, still using the just YouTube and Netflix.
This is the custom Sony X1 chip they use... which I have not been able to find spec on (have not thoroughly dug hard enough admittedly). But when I search, it seems to be 'clouded in mystery' like most TV makers spec. Some think it is ARM based, but everything is all on one chip, that much so far I know. It does have 10GB of storage, well about 8GB effective.