I have the DSA815-TG and I am very happy with it. The tracking generator is a VERY useful feature if you want to measure the frequency responce of filters, etc, so don't cheap out and get the one without it! Keep in mind that the TG starts at 1MHz, not 9KHz which is the lowest frequency (specified) that this unit covers.
Some key features about the Rigol DSA are:
* 9KHz - 1.5GHz Bandwidth
* Built-in preamplifier (often overlooked, but very useful)
* 1Hz resolution frequency counter
* AM/FM demodulation (not the greatest, but apparently this has been made better with a new firmware update?)
* Small, light-weight, and well built
One thing I don't like about this particular unit is its low input threshold of 20dbm. I highly recommend you purchase a good 30db attenuator and leave it perminantly attached, because if you don't, you can easily damage this sucker. Most SA's are rated to 30dbm which is much more forgiving, but still easy to overpower. On the plus side, it IS AC coupled, so you can have up to 50V DC without it causing too much trouble.
Another thing that pisses me off, is that all the advanced measurements are disabled by default and cost an extra $600 if you want them; I probably would never use them, but still. There's also an optional VSWR software add-on that will cost you about the same if you want it.