I have just bought a nice looking box of hamtaro cards, here's the breakdown:

12 cards per box
5 cards & 1 sticker per pack.

What to collect:
30 regular cards
4 rare cards (no odds given)
1 ultra rarecard (again, no odds given)
30 stickers
1 mini poster (per box)
1 Auto (of the creator, again no odds given)

Here's what i got:
Full set - plus duplicates.
2 rare cards
1 ultra rare card
27 stickers
no auto ( )

Now, the packs - although you only get 12 - are really cool because they are shaped like ham-ham! ears et all! but then it just get's a little, well samey.
The cards all have different scenes on with the number on the top right hand corner, flip em over and there is a map puzzle piece (get all 30 cards and create the map)...but whats the point because you get a map anyway!? then it just gets stupid because the stickers...are pieces of the map!!?? i.e. the same as the back of the base cards!?!? whats that about!? very odd
Luckily the rare cards are pretty cool: its is a close up of one of the characters with a glittery border and on the back info about them - not much different between the rare and ultra rare, but still pretty cool.
So, i would recomend them because A) They are cheap & the rare cards are cool & B) There is the chance of finding the auto, but thats it, base card under average and stickers just pointless.

I believe the release date was 2002, as noted on the wrapper and advertising inserts.

I opened one retail box (12 packs) a while ago and just opened one hobby box (24 packs).

RETAIL BOX: 12 packs of 5 cards + 1 sticker

Base set (30): 1 complete set, missing 6 for second, 3 threes
Retail Rare Cards (4): R001 R002 R003
Retail Ultra-Rare Cards (1): none
Parallel stickers (30): 12 different
Retail box-topper poster: yes
Advertising insert fold-outs: 12

HOBBY BOX: 24 packs of 5 cards + 1 sticker

Base set (30): 3 complete sets, missing 6 for fourth, no fives
Hobby Rare Cards (3): SR001(2) SR002(2) SR003(2)
Parallel stickers (30): 21 different + 3 dupes
Advertising insert fold-outs: 24