I've purchased the Nexus 7 twice, and I've sold it twice. The first time I sold it was when I purchased the Nexus 10... Then I re-purchased it a month later because I missed the small form factor for when I was out of the house. I then return it 7 days later (yesterday) when I jumped ship to T-Mobile and upgraded my Nexus S to the Nexus 4. The Nexus 4 made the Nexus 7 a redundant piece of technology and also out performs it by a large margin.
The Nexus 7 is a great piece of equipment for the price.. I will give you the pros and cons..
Cons
* - Audio quality via the headphones is awful. There are a ton of apps claiming to make your headphones vomit rainbows and unicorns but those types of app packages I steer clear from as I don't believe in them as from past experience they never work. DAC matters not the app.
* - I/O speeds are slow.. You can see a side by side comparison I posted of the read/write speeds between the Nexus 7 and Nexus 10
here. It can be slower to load apps/games than you might expect a tablet to perform. It's not bad, but compared to other devices it's noticable.
* - Color reproduction isn't the best.
* - (opinion) The Tegra 3 I wasn't impressed with.
* - No rear facing camera
Pros
* - Size: If you have no other tablet or a Smartphone with a large LCD like a Nexus 4 or GS3 then this will be a great portable device for you to get stuff done with.
* - Price: Currently what you get for the price is a good bargin. The longer its on the market though the slimmer this "good bargin" edge becomes and inches closer to being just another tablet on the market in a price range. It's still a great bang for the buck though and not much competes with it.. Yet...
Nexus 7 is exactly what it was aimed to be.. A good performing tablet on above average hardware for the price. You miss out on things like high i/o speeds and a rear camera but you have to give some things up for the $249 price tag.
Nexus 10
Cons
* - Same bad color reproduction the Nexus 7 had.. It's not a deal breaker but it's obvious.
* - The general consensus is don't buy them from Google directly. Find a retailer as it will make returns easier if it's defective.. Some believe the N10s have a high defect rate, some believe they don't.. It's currently the elephant in the room in the N10 forums. I wouldn't let it keep you from buying one but just be aware the concern exists.
* - Size.. It's 10 inches.. Some people think that this will never be a concern for them.. Until they get it and try making it a part of their daily schedule.. It's not meant to be throw in your pocket and carry around as a day planner.. It's big
* - You can't play Tegra HD games
* - It ain't cheap
Pros
* - Speed.. Speed.. Speed.. Mother of god is it fast
* - Resolution speaks for itself.. The screen is incredible
* - Battery life considering the pixels and speed the processor is putting out is fantastic. I average 8-10hrs of screen on time with non-gaming casual use.
* - Audio quality is excellent.. Woflson DAC on board.. No need for magic pills and As Seen On TV products to make it reproduce audio at high quality. The onboard speaker quality is really good also.
* - Gaming performance is excellent and far out performs the N7
Summary.. It depends.. If you plan on upgrading your phone (no idea what you have) soon I would go the Nexus 10.. Like I said.. Soon as I got my hands on a Nexus 4 the Nexus 7 became instantly redundant and outdated. The only thing sacrificed was 2.3 inches of screen but I gained ten fold in performance, screen quality and audio quality...