I was lucky in that this pack came included when I bought my toothbrush. Having used it for a couple of years now I definitely wouldn't buy one.
Firstly, I find the price too expensive for what you get, though perhaps comparable to other toothbrush heads. Secondly, I find that the FlossAction head (not included) that I mainly use does the same job as the tongue scraper. The tongue scraper also doesn't fit in my carry case storage bit that is attached to my base. With regards to the interdental spike, I have yet to find a use for it. It is too soft to poke anything out of your teeth and not a brush so doesn't clean.
The interdental brush is very useful though and I like it for getting in between teeth on a regular basis. It doesn't replace flossing and since I now use the excellent FlossAction heads I use the interdental brush less but it's still very good for specific areas.
In conclusion, the pack is not worth buying if you regularly use the
Braun Oral-B EB25-4 FlossAction Replacement Rechargeable Toothbrush Heads 4 pack. It might be worth buying for the interdental brush (this should really be sold separately) since it is genuinely useful but considering the cost of the pack it makes purchase prohibitive. Buy with caution.