I strongly reccommend one. The coleman also has a groundsheet for the porch, which the Coleman Epsilon didn't.I like the idea of a porch Mile 195
The two doors is a real bonus too. The side opens out which is great for getting out of when the porch is full of your stuff.
The pack weighs about 2.5kg, and if you want it's big enough for 2 people, although it is a bit "cosy". I have been in mine during some absolutely torrential downpours and it is unfailing on the water-resistance front.