Sporky - Vanos began on 1999 540s
Vanos on the intake valves only was introduced on the 540 in the 1999 model year when the change was made from the M62 to the M62TU V8. So if you want to avoid Vanos, as Sporky recommends considering, you need to stick with 1998 and 1997 MY (in the USA).
I think you should consider the contrary - avoid the earlier 540 and go for the 1999 or newer. THe M62TU is rated at the same 282 HP, but at a lower peak RPM and with 324 (or thereabouts) lb-ft of torque at a lower peak RPM than the pre-vanos 540's 310 lb-ft. Hitting these peaks at lower RPM translates into more area under the power and torque curves, which means more usable Jizz from the engine.
Still the M62 has a cable-operated throttle, whereas with the M62TU it is an electronic throttle. Some say the electronic throttle isn't as responsive as the cable one on the M62. Many schools of thought, so drive as many different 540s as you can and then make up your own mind. I test drove a 1998 540/6 minutes before test driving my 1999 540/6 and I felt the 1999 was noticably smoother, quieter, faster, etc.
2006 Honda Odyssey EXL-RES
2006 Honda Accord V6 EX-L Sedan
1999 BMW 540i 6-Speed (Sold to M3UOND on 9/21/06)
1991 Honda Civic Si - Occasional Beater