In my opinion?
Get it! It's good!
It comes with a LOT of stuff missing from the main product.
It deserve the price, if you consider that just one character portrait might cost you the same amount of money.
It contains a bunch of that kind of portraits plus tilesets, music, scripts, sprite sheets, battler pictures... get it already! :P
Here goes my opinion on this:
RPG MAker VX Ace comes with no modern day tile sets and the basic tilesets it provides are not so pretty.
Just look at the edges of a hill made by them in a game Black-squared unpolished.
You can always fix a tileset using a picture editor but still it is a pain.
Now DS+ comes with modern tiles of great quality, while it gives a bunch of usable tiles for decent outside mapping. It's as you can see on the provided pictures.
Not to mention that it contains some futuristic tiles.
Inside it you will find:
A] Two video tutorials .One on importing assets and one on shift mapping (very useful).
B] 20 background music pieces in ogg file format (correct looping)
C] 23 Battle backgrounds
D] 43 Battler pictures.
E] 124 cute battler pictures.
F] Pools, doors, gates, a pigeon, a pond, a sewer leaking tube and a lot of character sprite sheets to give great and appropriate animation to this DLC assets.
G] A good bunch of face sets.
H] Picture of hero portraits with expressions
I] Ballon pictures with emotions
J] Tilesets for: Sewer, City outter, Futuristic spaceship inner, landscape outter, inner volcanic, inner house, inner modern day, outter and inner ancient samurai or something, ship, modern hospital... it has really whatever is missing in my opinion from the main old product!
K] A sample game with used assets
L] A lot of quality scripts that come with instructions.
Now... all these come with the RIGHT to use them to create commercial games with RPG Maker series products, as long as you give credit to the creators (instructions for proper credits are included for every asset).
And there are still people that thing that this is uber expensive...
No. This is a really great DLC value for money. It really gives more value to the main product and it is a MUST buy in my opinion.
Do I recommend it? Of course I do!
There are also discount periods you can get it, but if you consider helping people that develop such great assets, you can get it anytime.
28 Euro is really a cheap price anyway.