[Milestone XT720 Themes and Apps] syrenz:
I'm making this thread both to share what I feel are good apps and to discover other apps for myself. I have not installed Dexters 2.2 or rooted yet (though I intend to) so I'm not going to list anything that requires it, but feel free to do so yourself.

So:

Lockscreen: GOTO Lockscreen. I saw this a while back but never actually checked it out. It was featured on DroidLife today so I decided to check it out now and it's great. Great, elegant look to it, great functionality as well. I've been using WidgetLocker for ages and it doesn't compare. There were some issues at first but after rebooting everything seems to work perfectly for the most part(I saw someone mention this as well in the comments so I did it). It's also on sale right now. Might be a bit of a drain on battery.

HomeLauncher: LauncherPro (Plus). I love the look and functionality of this and most of all, the widgets (which are greatly enhanced by Signal's themes -that can be found in Android Themes section). Truth be told, ADW (/ADW EX) probably has more options and functionality at this time (and you can use Colorize Widgets app to replace LP widgets for free). For now ADW might be better, though I'm just waiting for LauncherPro rewrite to happen (going so slowly). GoLauncher as well is fantastic. As is Zeam. There are many great options right now (and so many more on the horizon).

Whatever the case, something that is crucial when using one of these (at least for me) is to select the option to "Keep in memory." I think all of the above have that option (not sure about Zeam). My biggest issue with launchers is that my screen always redraws itself so much (this is a problem with XT720 stock launcher as well), so I have to wait forever for my icons and widgets to load itself, which is really annoying. I've tried things to reduce it, but the only thing that ever got rid of it was to select that option. Now using LP with that option and no lags at all.

I also recommend getting home switcher for easy switching between launchers.

EDIT: SPB Shell 3D

Keyboard:

Stock XT720 keyboard isn't bad (for me). I tend to alternate between that and Swype. I prefer stock keyboard for use in landscape mode. Once I'm rooted I plan to install that app that lets you choose a keyboard for portrait mode (i.e that would be Swype for me) and another in landscape (stock).

EDIT: Stock Gingerbread keyboard

Music Player:

Stock is decent, but nothing special really. I do like the album cover flow in landscape mode though. I alternate between that and Connected music player, which is the ripped music player from the atrix and droid bionic I believe (I'm not sure where to get it since that thread has since been locked). Winamp is also pretty good. PowerAmp has a lot of features, but you get annoying popups after two weeks unless you buy the full version ($5). I'd love to know what others use.

Some apps specifically use stock music player so that's another reason I use stock. i.e. when using GoTo lockscreen, the lockscreen changes when you're playing music to give you music player controls, but only seems to do when using stock music player.

EDIT: Google Music/ PowerAmp

Browser:

Stock is not that great. Has that nice bookmark cover flow in landscape mode, but in terms of functionality there are better ones. I use Dolphin Browser HD now (blue theme). Best UI for browser out there currently imo. A lot of people seem to love Miren and Dolphin Browser mini, for reasons I can't understand (everyone says they are super fast but I never notice any difference on my already fast browser).

EDIT: Opera Mobile

Games:

Really loving Stupid Zombies right now, it's a lot of fun (though has slow loading times). Ninjump is great for quick little fun. Angry birds also remains fun, though repetitive. Would love to see what else runs great on XT720.

Customization/Widgets/:

Beautiful Widgets is great and has a huge range of themed clocks and toggles. The recently introduced "Super Clock" was a great improvement. So much customization with this. Colorize Widget is great if you're using something other than LauncherPro, Signals has themes for it also. Widgetsoid and MySettings, are great for quick access to settings.

Task Switching:

SwipePad is just phenomenal and has a great UI, I recommend you check it out if you don't have it already. Together with long press on home button, I have amazing task switching going on.

File Explorer:

File Explorer is a must for me on my XT720. It's how you can install APKs and browse your sdcard and everything and change things easily. ES File Explorer is great for that and has a nice UI.

There's more that I wanted to add I'm sure, but here's this for now. Feel free to share what apps you use on your XT720.