Mark... Nice description of life with Sky Commander.
I've been living with one for several years now and I too suffered from "sluggishness" during cold observing sessions. The problem is that if you don't run 12VDC to power the setting circles (which it sounds like you are) the display heater doesn't run and you will definitely suffer from sluggish display response in cold weather. As it turned out, my problem was that I had a poor connection to my 12V bus. It was a plug configuration that was coming loose during sessions. And when it got cold it got so bad I was putting hand warmers on the display face to make it somewhat useable. I've since permanently attached the power for the DSC to the 12V bus. I no longer have the problem with sluggish display. If it's "stupid cold" (below 10*F) it slows down a bit. But nowhere near as bad as when running on the internal 9VDC supply (no display heater running). Have had no problems in more civilized temps (below freezing into the teens). Mark... If you're suffering from a sluggish Sky Commander with 12V plugged in, you may want to check that connection.
As for the limited catalog space. This was actually an issue that got me thinking about switching. But after looking at Argo Navis I discovered they too suffered from limited catalog space. They don't have complete UGC and PGC catalogs. For that matter, sky commander gives you more flexibility in which catalogs are loaded than Argo. The problem is that you're dealing with only 512kb of space and that's not much. I played around with loading different configurations of catalogs and was never really satisfied. Have since gone back to the default catalog set and will either star hop or key in RA and Dec if feeling particularly lazy ;-) . The Nexus DSCs are probably going to be the "cure" for those of us looking to have our scopes do go-to's to really obscure stuff without star hopping or manually entering coordinates.
Ivan... Personally haven't seen much of a difference between ground conditions. But, I haven't really been paying much attention to that variable. I do know that some nights are better than others when it comes to pointing accuracy. Am going to have to start paying attention to my ground conditions to see if that's making a difference. Could be...
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