I'm flying into Rio (from the USA) in the near future and am thinking about taking a couple new in box ipads with me. Not sure of the legality of it but am more concerned with getting them taxed or confiscated or something. I've been to a few countries in Europe and have never had my bags searched (at least by my knowledge). Just wondering how strict they are or if its just a rubber stamp process usually.

They usually X-ray bags these days. I haven't had them search bags by hand for awhile, going through the 'nothing to declare' line, although they are likely to pull aside some Brazilians coming home who they suspect have gone shopping. You are allowed (iirc) to bring in $500 worth of stuff. I would take the iPad out of the box and perhaps put some sort of personalized wallpaper on the screen to show it was used and for personal use. I would not suggest bringing multiples of any electronics; this indicates 'for sale', not 'gift'. If they decide to tax anything, it would help if you had the original receipt to prove value; otherwise they can pretty much value it at whatever they think it's worth (top value, not discounted or sale price) for tax purposes (and the tax to be paid would be close/equal to the value placed). Depends on how comfortable you are with financial risk I guess.

Thanks for your advice. Sounds like maybe I should just bring one ipad, no need to be greedy. Although it will only net me $300 thats better than losing money. The only reason I was so concerned was because last year I mailed a girl in a rio a t-shirt (not designer, just one from my local print shop) and a $40 charging battery for her iphone. I think she had to pay around $40 in taxes to even pick up the package. Completely ridiculous!

If you have 2 of something you are at risk.

Taxes are high in Brazil. The same model car that costs $20K in the US costs double that in Brazil, for one example. That's why electronics are so high too.

For mailing, if you keep the total of the declared value (on that green slip the PO attaches to the package) plus the postage to under U$50, it usually doesn't get taxed or flagged for taxing (but of course if it gets stolen, you have no recourse for a claim for replacement value since you have undervalued the item on the declaration form).
Otherwise, Brazilian customs is not letting much slip by these days (used to be, certain addresses/locations didn't get checked); all is taxed (declared value plus declared value amount in taxes).