Okay, positives first. The bag is strong and fits the amp perfectly. There are a couple of pockets to fit extra gear, notepads, cables in.
There are some nice velcro straps that keep the bag on and hold back the main cover when you are playing on the street.
The bag seems really waterproof with sealed zips but I haven't really tested this out because I live in Spain and it doesn't rain much. I bought the amp last year and was carrying it around the streets without the bag. It is definitely easier to busk and travel with the bag.
However, whilst the bag seems really well made, it is not a thick material and has no padding. Yeah it seems strong and durable but perhaps a little overpriced.
It is a shame that the amp does not come with this bag. I am not entirely sure that the bag is worth the money is costs to buy but I am happy I bought it.