A factory reset only wipes the /data partition on your sd card. That's all the apps and settings you installed after taking it out of the box.
So a reset might help if your problem is caused by your apps or settings.
The lag and slow browsing unfortunately is inherent to the stock rom. Something to do with the I/O performance.
The only way to fix that is rooting and installing Browser2Ram or a custom rom. I can understand that the idea of unlocking etc is daunting - I felt the same way. But man! It's worth it! I am running a custom rom now (CROMI) and it's as if I got an entirely different and new tablet here! No lag, no fc - just pure speed and beauty.
No warranty either - yes. But I rather live with that than a tablet that is running on 2 of 6 cylinders.
But that's a very personal decision....
You can hold out and hope that when and if Asus releases 4.2 some or all of your trouble will disappear, but reading the Nexus 7 forum and their experience with 4.2 - I wouldn't hold my breath...
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