Don't shoot many comps but I have used my Fox carp bivvy along with my Fox fishing chair - super comfy chair, the bivvy keeps out the worst bad weather and is a superb shade in the current scorchio sun. It assembles very quickly, can be set up as an open fronted shelter or a fully enclosed tent and the zip off front panels can be rolled & tied back to allow various levels of access. Mine has adjustable vents to provide some air flow too, assisted last weekend by a cheap solar powered fan.
In the event of mishaps they are easily patched or repaired - anglers can be a clumsy bunch - so should give many many years of solid service.
They are pricey to buy new (up to ?350) but masses of Fox and Fox-a-like bivvies come up on eBay every week and go for ?30-?100 ish depending on what you want and how heavily you intend to use it.
Karl