I personally don't believe in any laptop as a desktop replacement. In my opinion, the 3790 doesn't even come close as being a desktop replacement, then again it all depends what exactly you use on your desktop.
For an example, on my desktop, I'm running a Pentium 4 3.2 ghz prescott cpu with 1 gb of ram, 9800 pro, two 73 gb scsi hard drive and 1 200 gb sata hd, 1 dvd drive, 1 dvd burner, tons of fans but ball bearing so it's fairly quiet, and a 550 watt thermal cooled psu, and a 22" crt monitor.
I personally prefer using my desktop but I just need a basic laptop to haul around when i'm not at home. My 3790 is 2 ghz and it doesn't even come close to my desktop's performance, but to me, it's superb and gets everything done.
So no, I don't think the 3790 is a desktop replacement, but more like a supplement.