We did this in October and December 2000 in a Landrover, with no probs whatsoever. From the immigration book, they seemed to get a couple of overlanders a week through here. Border crossing very quiet, extremely nice man on the indian side - you could almost miss the immigration post.
I seem to remember having to cross a singletrack bridge/dam in no-man's land, which you may have to pay a small "fee" for.
On the Nepal side it's even more relaxed, we had to show the customs guy what to do with our carnet! Immigration just a kind of shop front, about 100m from customs post on the left. Next door is a tourism office of sorts - they gave us a map and changed some money at a reasonable rate. From there the road is now excellent all the way to Bardia N.P., which I would highly recommend. Beautiful, friendly, relaxed, oh and you may see tigers as well! What more could you ask for!
We crossed the border and made it all the way to Bardia in a day, doing about 80km/h. The scenery is out of this world, the villages are like a scene from the English Middle Ages.
On the way back, we had a few problems as there were local protests about something and roadblocks in most of the towns, but we managed to get past by driving through bits of jungle! Fill up with fuel where you can too, as there were a few shortages. Can usually get it out of a barrel somewhere if the pumps are dry. As the Nepali currency is tied to the Indian rupee there is v. little diff in prices as you cross (as I remember, someone correct me if I'm wrong!)
The Indian drive to/from Delhi is not as nice as the roads are pretty awful, and the maps aren't all consistent. (we were using Nelles plus the Footprint India handbook which had some small maps in). But hey, that's India...