I added a Caldwell Bipod to my GSR last weekend. So far I like it a lot- it's a lot of fun. It attaches/detaches really easily. It extends from 6-9" and weighs 12 Oz.
It's a toss up - the bipod is fun but I really like how sleek and maneuverable these rifles are before all the attachments.
Hopefully I will find a nice LER scope soon- I think it may be the winner. Between the red-dot and the peep sights I think I like the peep sights best. Plus they don't need batteries!