I'm a PC gamer and hear nothing but complaints about it.
The mouse is fine; I have it set to high DPI and get very little lag.
I'm sorry, but you don't magically not have input lag when everyone else does, and the fact is you know this or you wouldn't have had to admit to there still being a little. There shouldn't be any, especially when not everyone had a high DPI mouse, let alone the fact that many generic (and the most prevalent) mice only have one setting.
The game UI is very unintrusive and the menus work great.
Yes, in your magical world the issues with the menus don't exist. I'm sorry, but I don't buy it. Even reviewers have noted that the menus will exit out or select the wrong option when clicking on another option entirely, others have noted that something the menus selections fail to change or get get stuck on a selection refusing to move from. I'm so happy that you and a few other people magically don't experience the various very real issues with the UI that even professional reviewers have outlined in detail, not even counting the forumites having issues with it.
What exactly is the problem with it? Read a review. There are entire lists.
The game is great, but pretending that the flaws it does have 'don't exist' does help anyone. It's a great game with a few flaws that Bethesda need to know about, and that are likely quite fixable, but they are real and well documented flaws at this point.
I love the game, but only a mindless fanatic can't see that it has its issues. Instead of going, "You guys have problems? I don't so there must not be any problem." how about just lending your support to the people that do have actual technical problems instead of just making it harder for them by lending support to the idea that, "If it's broke for you, it's fine as long as it doesn't affect me."