Hi RPO,
I bought a '99 528i about 2 years ago and love it to bits. It is a very smooth, comfortable ride. I also love the E39 shape - it is still a very good looking car - didn't win world's best executive saloon title for a number of years for nothing. I got it with about 145k km's on and have taken it up to about 175k. I have had cooling system issues (see my other thread here) ever since I got it, which it turns out might have been caused by a cylinder head issue all along. If you can be confident that yours has had its head / coolant issues thoroughly worked out, then I would say go for it. General consensus is also to make sure that the water pump is in good condition.
There are some reports of the auto box failing when entering the high mileage zone (160k km's+), but these are sporadic and apparently can be prevented by having a proper fluids service done on the box - contrary to BMW's "lifetime" fluids philosophy. Do be wary of this one, as I believe a replacement box is in the region of R50k.
Performance is surprising when on the freeway, more than adequate for most purposes. The only niggle with my auto is that there is one particular point in the power band where there is a very slight flat spot, usually encountered when filtering in on the freeway (say 60 to 70 km/h). Easily worked around by planting it a half a second or so in advance :thumbsup:.
Other minor niggles with the E39 are the seat trim / electrical connectors for the electric seats - these break if not properly cared for. I'm currently shopping around to get mine replaced. Pixels on the console displays can also fade / fail - I'm not sure how readilly available repair services are for these locally, but I think the dash has to come out to get it sorted, so I just live with it.
If it has the standard 16" wheels, the correct 225 tyres are expensive - I paid R8000 for a set of Michelin Primacys for mine recently. It would probably have been cheaper to get alternate 17" mags and appropriate tyres, but at the time I wasn't in a position to shop around.
On my unit, I do encounter a fair amount of body roll when cornering, but I suspect that this is normal for a car of this size + my suspension hasn't had any attention since I got it.
These minor issues are amply compensated for by the comfort and performance you get from the car - the ride inside is whisper quiet until you put your foot down, then you just hear the sweet straight six singing its beautiful music. No wind noise, no outside traffic noise - it still sometimes surprises me.
My fuel consumption is high (currently 13l/100km), but I think this might be due to a combination of mostly enthusiastic city driving and possibly my cylinder head issue.
This car converted me to a BMW fan and I'm currently shopping around for a slightly newer model, as you just get so much more car for your money than anything else out there. Since it is not quite so popular as the 3 series, good bargains can often be had.
Good luck with your purchase, hope this info is useful!
imp