It really depends on what you need. I love apple products but have been holding off of the iPad because I don't really have a use for it. (I did buy a new air though
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I have a ASUS tablet and have been using it for about 3 years. I has a stylus which is key in my opinion. I use it for taking notes on OneNote that gets sync'd back to the servers when I am back in the office, I also do diagrams in Visio so I can show clients designs right on the spot.
It's handy to have a full blown (win7) PC as I use it for VPN'ing in, wireless site surveys and wireless site drawings along with all the office stuff.
The only negative about my ASUS is it only takes 2G of RAM, other than that it's been great.