I think the first part is corny, misguided garbage. The "books of Saxon" prologue and Simm's overacted monologue about everything he wants to eat stand out as particular low points. (note: this is based on my one and only viewing of it from almost 9 years ago. So I haven't obsessively watched it again and again; it was just that bad to stick into my memory ever since!)
I actually like part 2 though. Other than that ridiculous scene of Tennant spinning back and forth between the Master and Rassilon, re-cocking the gun each time lol. But contrary to others, I do like the whole goodbye tour and "I don't want to go." And the four knocks reveal is, I think, the best executed moment in Doctor Who.
The first part of The End of Time is
classic RTD in that it's really, really good ideas but rushed to the screen and so not expressed well. Like, the concept that RTD puts forward of time travel and linear time in the Doctor's life - this idea of how despite having a time machine, events he is directly involved with still have a timer on to him - is really great. In the script, the way the sequence where he lands on the Ood planet, realizes the Master is being revived and tries to rush to stop it but is too late because of his own idiotic delaying - that's a really well-written piece that's fascinating in terms of implications for how the Doctor lives his life.... but on screen, it doesn't really come across as
anything.
Then there's just stuff like the Master as a hobo... it's a great idea, this pompous character reduced to living on the streets, unable to claw out any other existence because of his face, because he looks and sounds like a murderous ex-PM. But the original versions RTD was pondering, the stuff that would've made it into Torchwood (ie The Master luring a rent boy into a public toilet before killing and eating him) is, again, probably better than the lightly-censored stuff we got. But it's full of these great moments, too. Everybody remembers the scene with Wilf and the Doctor in the cafe (and the later one in the ship) because it's an all-time high, but I love the moments like when the Master realizes the drum beat isn't just him. "It's real!!!", I love the Vinvocci as a benevolent alien influence, etc.
Books of Saxon is obviously flim-flam, but it's needed to get you there. And again, I love elements within that scene. I like the idea that Lucy resists, that she sabotages his revival. It's the classic RTD thing, like I say... underneath the rough edges there are wonderful character beats.