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Nice review. I have no experience with the Astro Trac so good to read something about it.
A few additional points regarding the Polarie. You can get a cheap USB power supply off ebay for $30 or less, say a 5000MAH unit that will plug into the Polarie and you can stick it to your tripod with some Velcro. It then will run all night.
Polarie used in a horzontal orientation now becomes a panning unit for Time Lapses and is very good for that. You can also simply reverse the panning direction by flicking the switch from southern hemisphere to northern hemisphere.
The half speed tracking option is handy for a compromise between foreground and sky if you want sharper foregrounds.
I have no joy with polar scopes in the past but the Polarie unit is actually very easy to use at a dark site. You just need a dim torch to illuminate the reticle or put some tissues over your torch to dim it. I can get a very accurate polar alignment with the excellent instructions in about 5 minutes 10 minutes tops. It will then give up to 6 minutes round stars at reasonable focal length.
Additionally the Polarie has a nice optional extra which is a compass and tiltmeter that fits onto the hotshoe. I have one but haven't used it yet. It would mean you don't have to take the camera off which as you point out is a bit of an annoyance.
Just for the record you don't need an expensive ballhead. I think the one I am using cost less than $100 no need for a $545 ballhead!
A $545 ballhead defeats the purpose of a cheap but effective portable mount.
I got a carbon fibre nicely made Chinese tripod including a nice smallish ballhead (very easy to use and totally adequate) off ebay for $228. I was surprised at how well it was made. It is half the weight of my Manfrotto aluminium tripod and just as stable.
If you use a heavy DSLR and lens on Polarie you need to use a pair of pliers to tighten the tightening screws because if you don't it can slip around once the angle is sharp enough.
I also bought a cheap digital inclinometer for the Polarie to get the angle very accurate and that only takes about 1 minute or less. The little illuminated one on the side is too small to see easily in the dark to be that useful.
So keeping in mind the above the Polarie wins on more counts. The Astrotrac looks good but for my use the 2 hour limit meant it was not suitable for time lapses which are often a 5 or 6 hour period.
Greg.
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