I have a Samsung Galaxy Tab 2 7.0, and I find it pleasing to use and it runs Ice Cream Sandwich, which is better than a tablet running 2.3 (DON'T run a phone OS on a tablet). 4.1 is better than 4.0 in every way, especially when it comes to performance, though. Good thing as mine's going to get it sooner or later.
The Nexus 7 sounds nice, but you lose microSD and rear cameras... The screen on my Tab is nothing to write home about, and it's a bit of an old model at this point, but it's still heaps better than these cheap 4GB tablets that are there for... nothing. Then again, I could be biased as I was given a 16 GB card as a free gift, making me end up with 24 GB...
I'm leaning towards the Nexus 7 as it runs Jellybean, not sure if you care most by the latest OS version like I do. xD But yeah...it sucks to see that it does not have microSD card reader, when most if not all tablets should have that. (I'm trying to process the fact that tablets include flash memory lol).
I was told Lenovo's tablets suck, as they're too glitchy and they lack updating. So you're better off sticking with the Nexus 7.