It's too bad that they are dumping the Sirius polar orbital satellites as they were so much better for driving around.
The XM geosynchronous were better for home, though, most people don't have a home satellite setup.
I, too, notice that my SXM (XM side) drops out when it really shouldn't. I get it if I'm going down a road and there's a thick canopy of trees or a mountain beside me (again, the Sirius satellites generally worked in that situation). A lot of the time, though, it just drops and has me thinking, "Why is it dropping out, now?"
To be fair, now that I think of it, it could be the buffer that's the problem on the modern radios (built in radios are very likely buffer free so this wouldn't apply): Let's say you have to stop under an overpass (no signal but you're 10 min behind in the buffer and then 10min later, out on open road, you hit that spot and, without thinking, wonder, "Why is it dropping out??"