When I first bought SH4 and found myself in the middle of a cow feces throwing fight between Sony and Mark Russinovich I was pretty disgusted with UBI for using a copy protection scheme which does not allow a computer to run a program (Process Explorer) just because of who the author is, not because it is useful to illegal disk copying. I was ready to sell the game on eBay.
But I made the mistake of uninstalling Process Explorer and trying the game.
It is an absolute hoot to play and the longer I play, the better I like it. Sure, I'm looking forward to whatever improvements come with patch 1.3, but I don't think it is fatally flawed at all. I believe mostly those with stability problems are playing with marginal machines (less than 2 gb of memory, older graphics cards, Windows Vista (hehehe) etc). For me the game has been rock steady with no CTD's at all and no save game problems similar to SH3.
I'm running an AMD Athlon 3700+, 2 gb OCZ go-fast memory and 2 EVGA GeForce 7600GT 256MB graphics cards in an SLI configuration (saved me a bundle over one 8800 card and runs like a scalded dog). So I sacrificed processor speed for graphics and have a sub $1000 machine that runs either Silent Hunter with graphics WFO.
I'm looking forward to improvements in the game, but far more important are improvements in myself as I progress toward running both games on full reality settings. SH3 with GWX is ultimate training for dealing with destroyers. If you can survive that, you'll prosper easily in SH4. I'm having a great time and recommend both simulations highly.