A bipod will help if you intend doing a lot of prone sniping, but it does add quite a bit of weight to the front end. Personally, I'd go either for the under-gas block rail adapter or the bipod type that clips into the receiver to bring the extra weight of a bipod back a bit. But then I haven't fitted one to mine, as all the wrappings on the front end make it difficult to access the front end anyway to add, or deploy, a bipod.
As for any airsoft sniper rifle, there isn't anything OOTB that is really good, apart from TM products, which are way too expensive and low powered, or a Real Sword SVD, which is also VERY expensive. Almost everything else needs money spent on it to make it a good, accurate (as much as any airsoft gun can be), skirmishable weapon, from hop units and trigger mechanisms to inner barrels. That said the A&K SVD does take AEG springs and inner barrels, so you are not limited to the sniper specific upgrades that most other sniper type rifles require.
I quite like mine, but as someone said previously, it is long and gets heavy during a long game, so a sling is a necessity. However, I had an L96 a few years back and that felt really heavy after an hour or so. If you want something light, go for a clone of the M700 sniper rifle, as they are nowhere near as long or heavy, but will still need a lot spent on them to bring them up to scratch.
And as for the CO2 kit, yes it does make it a lot lighter to cock, but the downside is that it's a pig to have to change between the different parts when out skirmishing and it can be quite a process to find a spring strength that will give you a site legal FPS when using it. I have put together a totally separate CO2 kit for mine, where I replace all the bolt section with the CO2 specific parts, but getting the FPS to just below 500 is proving quite tricky at the moment, as the strong spring with the kit pushes out anywhere from 550 - 600 FPS on a new bulb and the weaker spring struggles to get over 350. More work needed. <_<