According to most owning a 4-Matic is risky business.
When the transfer case develops the dreaded internal leak (hydraulic fluid seeping into the ATF side of the TC) you're in for a very very expensive replacement if you want to keep the 4-Matic feature. It is my understanding that 100k miles is the threshold at which most problems begin.
I've had my '93 300E 4-Matic for 19 trouble free months now and I can't describe how much I like to drive this car in the winter. It only has 73k miles and hope that the TC will hold beyond the 100k miles mark. When the TC goes I intend on switching the 4-Matic system off and drive it as a regular 2wd.
In the meantime I'm enjoying the heck out of it.
I hope this helps.
'93 300E 4Matic
'98 Nissan Altima
'00 Yamaha Road Star Silverado