I've been using the cradle and bundled battery packs for a little while now, and I'm happy enough with my purchase. Overall, this is a very competitively-priced product: a decent alternative to Microsoft's own-brand kit.
The product spec neglects to mention that each battery pack is rated at a capacity of 900mAh. You will therefore notice that they don't provide as many hours of gaming as you would get from alkaline AA batteries, or even rechargeable NiMH AAs (typically 2000-3000 mAh). Venom are hoping you'll like the benefit of never really needing to remove the battery packs from your controllers. Rechargeable AAs are fundamentally better batteries, but if you don't want the hassle, these packs do the job.
As another user has noted, it's not possible to charge standard Xbox battery packs with this cradle.
In the packaging, you'll find a cradle (finished in a high-gloss black plastic), a USB cable (for connection to your Xbox, or other powered USB port of your choice), and two rechargeable battery packs. It does not come bundled with a power adaptor, or an instruction manual, though neither is really necessary at this price point..
The cradle is rather light, but does have non-slip feet attached, so it shouldn't move about too much during use. It is powered by a USB cable (male type A to miniUSB), of generous length. The USB ports on the new Xbox 360 S remain powered even when the console itself is on standby, so all works a treat. If you have an older 360, and your USB port is occupied by the wireless adaptor, you'll need to find another powered USB port: Veho do a great 3-pin plug adaptor, which has a single integrated female USB port, typically for less than a fiver. Job done!
The cradle has two slots for controllers. Each slot has two spring-loaded metal prongs, to connect with the contacts on the battery packs. The connection feels a little flimsy (and it might take a couple of nudges to get the controller to charge), but again, no complaints for this price.
The battery packs themselves are unremarkable: the release catch seems sturdy enough. I noticed that initial drain (time taken to lose one 'bar' of charge) happened considerably more quickly with these rechargeable packs than with alkaline AAs, but have not had any of my kit long enough to have drained any batteries at all, so I'm not in a position to comment on the lifespan of a charge.
You'll know when your batteries are charging, too: wave goodbye to your eyesight with two retina-searing green LEDs at the front of the cradle. This could be a bit of a distraction if the cradle is within your field of vision when you're gaming or watching TV, but it's easily rectified.
In summary, cradle might be a tad flimsy, and the batteries might not be blessed with all that much in the way of capacity, but together, they certainly do the job, while saving you a bunch of money. Recommended!