Realistically will you eat the contents every week? If not is it a problem to cancel the occasional box. Assuming your box will be seasonal and local-ish (ours is) at this time of year we get a lot of root veg (carrots, swedes, parsnips etc) and apples.
If you don't currently eat a lot of veg etc, will you be likely to change your diet and incorporate new foods/recipes.
We have had a box for 4 years now. I do cancel the odd week which we are allowed to do. Ours costs £10 and we get on average 12 items, fruit and veg. A typical item might be 1 pepper, 4 large carrots, 4 apples, 2 large parsnips.
We are allowed to make special requests but generally just accept what arrives, I quite like not having to choose what we buy iykwim. This wouldn't work for someone who had a lot of likes/dislikes of course.
A big pro was in the Summer the most gorgeous local strawberries arrived. We also get fab mushrooms. Really fluffy potatoes for baking/roasting.
The cons - I have run out of ideas for swede.
hth.