Everyone had a great feedback.
I don't think I can't add more to it, but to summarize what everyone said.
Except the FN FiveSeveN, all my pistol is H&K.
1. Sight picture are usually lower on HK than other german/austrian firearms like Sig or Glocks
2. The trigger is really hard to master. My first HK pistol was USPc 357sig, and I was shooting bad grouping at short dist as 5yd. I realize that trigger pull is slightly harder to get use to than any other pistol. However, if you get to master it, USP lines are great pistol to have.
3. Double action trigger at NIB are not impressive, but as the time goes, it gets really softer.
I think USP/P2000 line of pistols gets much better as times goes. I would say, if I had USP tactical as my first HK USP line of pistol, it would've been far easier for me to get use to.