This addon is a unit frame modification (player, target, focus, party, arena, raid, and so forth). The purpose of the addon is to add critical missing functionality to the Blizzard unit frames and improve their readability. The addon modifies the Blizzard unit frames without totally replacing them.
Following are the changes, organized by the unit frames they affect.
All unit frames
All status bars now use flat textures for readability.
Text for debuff stack counts is added wherever missing (target of target, focus, and so forth). This is particularly critical for tanks, who, on tank-switching fights, need to know how many debuff stacks are on the other tank.
Player, target, and focus frames
Frames can now be placed wherever you like. Just right click on the focus frame portrait and select "Unlock frame". Then you can drag the player, target, and focus frames around. If you drag one of the frames off the screen, it will snap back to its SnowfallUnit default position.
Absolute, percent, and max values are displayed on health and power bars.
The proportions of the name, health, and power bars are changed. The health bar is now much more prominent.
Most of the text is changed to an ARIALN font for readability. I highly recommend that you take the further step of replacing all your game fonts with more legible ones. I use Calibri in place of ARIALN and Calibri Bold in place of everything else (see screenshot). Calibri is not free, but it is distributed with Windows Vista, so you may already have it available. This is an easy way to replace your game fonts without needing any addons:
Create the following folder:
<WoW directory>\Fonts\
Create four copies of the font file of your choice, place them in the above folder, and rename them to the following names:
FRIZQT__.ttf (the main UI font)
ARIALN.ttf (the normal number font)
skurri.ttf (the huge number font)
MORPHEUS.ttf (mail and quest Log font)
Target and focus frames
A class icon is shown above the frame. Note that Blizzard's definition of "class" for non-player units is different than for player units. Generally speaking, for non-player units, "warrior" means a high armor unit with no mana bar, "paladin" means a high armor unit with a mana bar, "mage" means a low armor unit with a mana bar, and "rogue" means a unit with an energy bar.
A race+sex icon (for player units) or creature type text (for non-player units) is shown above the frame.
Raid frames
Health and power bar borders are removed to improve readability.
Cast bars
Instant cast spells are now shown on all cast bars except the player cast bar. Try setting your character as your focus and casting some instant spells/abilities and you can see how this works.
Cast bars are moved above the corresponding unit frame.
Cast bars are shown for trade skills.
Configuration
There is no additional configuration beyond what Blizzard already provides for the unit frames.
Possible future changes
Add black status bar borders (like on the player frame) to the pet, target of target, target of focus, party, and arena enemy frames.