Well, its the fourth WP7 device I've owned, and I think its definitely the best.
Things I really like about the TII that NOBODY talks about :
1) There's more options for screen lock time - used to be you had to interop/developer unlock your device to change this setting in the registry - but the TII has the option to never lock the screen, or set it to 15 or 30 minutes. Like that HTC did that.
2) There's a noticeable volume jump from 29 to 30. HTC must've known if you set your volume to 30, you want it booming, because you can hear a significant jump in sound from 28 or 29 to 30.
3) Attentive Phone options - really nice to have, right in the settings.
4) Hearing Aids - I always had to have other WP7 devices at 10/10 to hear anyone, with the TII I use this setting and keep it down to about 6 or 7. Another nice feature.
5) Responsive capacitive buttons. Either I had problems hitting the Lumia 900's buttons or it was designed to be less responsive, but I could swear the TII responds better when I hit a capacitive button.
6) Notification LED - I love it. No Samsungs have it, no Nokias have it.
These are great features on top of some already great things like the curved chin which your fingers just seem to easily rest on, the great camera, and the large screen. The Nokia did spoil me with "Clear Black", and I like AMOLED screens better, but I also prefer using the light background (easier to read and I don't have great eyesight) - so the TII actually works better for my needs.
If I had to rank the WP7 devices I've owned, I'd go :
Titan II > Lumia 900 > Samsung Focus 2 > Samsung Focus