I have a Taig, its a great little machine. But, it is little, you need to size the machine to what you want to do. If you're going to limit your parts to about 7"x3"x2" then the Taig will be fine if you don't mind waiting an hour or two once you have it CNC'd.
But, since this is your very first mill, do not worry about whether its cnc ready, or how easy it will be to convert etc. You need to learn about metal working first before jumping to CNC or you'll just end up ruining parts and cutters before you learn the ins and outs.
Since you have $1500 to spend, I'd suggest an X3, a vice, some basic tooling and some stock and start learning on it manual first. Spend a couple months making little things and learn how to use the tool.
You'll need to learn how to take the machine apart, to clean it, how to adjust the gibs, cut down on your backlash etc.
Once you've learned the machine enough that you can quote your travels, backlash on each axis/where it is, the biggest cutter you can run and at what speed/feed as well as the smallest cutter, all off the top of your head then you're probably ready to start looking in to CNC.
The X3 is probably the best starter machine if you have the money, after learning it then you can start converting it yourself. Once you're ready to convert, and if you do it yourself, you're probably looking at $600-$900 more to convert it. But, you will have a nice machine that you know inside and out and won't have any problems fixing it.
If you just want to jump straight in to CNC, then the Taig is probably the easiest as it uses true inch screws (though this probably won't matter if you're outside the U.S.) and you can purchase then CNC ready machine for ~$1200, hobby cnc board (hope you're not afraid of soldering - $90), steppers of the 270 oz-in variety (~$60-$120), 36v power supply ($50), a computer with EMC2 ($0.00 but you'll need a decent understanding of Linux and some patience to get everything working). All of this will probably put you slightly over budget after shipping.
Next up would probably be an X2 with a ballscrew conversion (
here) then the same basic electronics mentioned above.
As far as how rigid the Taig is, while bjones here is being clearly inflammatory while offering no real help, I can tell you that dispite its size its a very stout machine. In fact, its only real failing is how little HPs the stock motor has. I've run some simulations on it, with ~100lbs of force acting on the spindle, the entire column/head assembly is only torqued a maximum of 0.0014" (1.4 thou), I don't believe the simulation is entirely accurate (I bet maximum deflection with that load would be closer to 8 thou), but I've noticed myself that the motor runs out of torque long before any scalloping occurs in the surface finish.