Hi
I've had my IS220D-SE for 3 months now - and still think it is a fabulous car - I pass lots of BMW's, Merc's and Audi's on my commute and I still feel smug cocooned in my well equipped and comfy Lexus.
There are pro's and con's for all the usual suspects, but IMO the Lexus, whilst not necessarily getting 5-stars in every area, ticks enough boxes enough of the time to beat the others.
Another facet that, whilst it didn't sway my opinion/choice but did confirm it, was the level of customer service I received when visiting the various showrooms: At the BMW garage my wife and I were ignored when trying to obtain details on a 320d and, when we did manage to draw someones attention they were snooty and pretty obnoxious. The Merc garage was worse, off hand and dismissive and didn't even send me the prices I'd requested despite a phone call to chase them up. They seem to forget that whilst I might be a 320d/C200 driver of today, I could be a 6-series/S-class driver of tomorrow. To be fair, the people at Audi were fine.
Sorry about the customer service rant...
The ML sound system is incredible (your rear view mirror certainly vibrates with Arcade Fire at high volume), plenty of go when required, soft leather, lots of toys and, yes prestige - all at a price that the others can't match.
I believe Audi are doing a free upgrade to S-line as they are in run-out mode, the BMW is for estate agents/wide boys and the Merc is for old men/drug dealers.
Get the Lexus, pocket the difference.
Oh... and you'll be let out at junctions