I had a SON (Schmidt Original Nabendynamo) dynamo hub, a Bisy FL-SR headlamp, and a B&M Seculite tail lamp from SJS Cycles; and some speaker wire and a cheap no-name switch from Freewheel in Reading - the total cost was about 145 pounds, although one could easily knock 60 off that by buying the Shimano Nexus hub dynamo - a perfectly adequate piece of kit, but the drag is higher when switched off than the SON. It is well worth paying the extra few quid to make every junction a soldered spade with heat-sensitive insulator shrunk about it (this rather cunning stuff shrinks by a factor of two when you turn a hair-dryer on it, making adding insulation trivial).
Older Nexuses had higher drag when switched off than when switched on, but luckily they don't make those anymore. Shimano's Nexus incorporates a switch with On/Off/Auto (light-sensitive) functions, which is certainly handy - however, there are reports of these frying, albeit not a significant number. These switches are separately available at about 15 pounds.
I've retained battery lights, although they are largely superfluous. Owing to a spate of breakages I now have a 2xAAA LED rear which is rather feeble, a 3xAAA LED Cateye TL-LD260 which is bright and not absurdly directional - and meets the relevant British Standard rendering it nearly legal; and a Smart 4xAA LED/halogen switchable - this last is rather nice, as it can aid seeing or being seen as needed.
However, if this would be your sole lighting system you would want instead a Busch & Muller Lumotec Plus or Oval Plus headlamp, which would add about 5-10 pounds depending on the model. These do not have quite as nice a beam pattern as the Bisy (although it is perfectly good), but incorporate a capacitor and an LED standlight that comes on when halted for about 3-4 minutes - adequate as a "being seen" light, and you don't need a "seeing" light when you're not moving. Similarly you would want instead a Seculite Plus rear lamp, about 5 pounds more, that also includes a capacitor (which drives the regular red LED when halted). The Lumotec appears to be the best standlight-equipped headlight available. I decided about three months ago that it had been a mistake to skip the rear standlight, and upgraded to a Seculite Plus.
Another option is to fit a 3W front bulb instead of a 2.4W front bulb, and use battery LED rear lights. In fact the 3W fronts are not noticeably more bright, but if you omit the rear lamp the wiring is much less fiddly, and of course losing the tail lamp renders the whole project cheaper by about 15-20 pounds. A 2.4W bulb will work in this setup, but will be fried relatively quickly.
Some headlamps can be had with an integral switch (adds about 2-5 pounds - some of them have switches and integrated light sensors as well, for an On/Off/Auto setting); the Lumotecs and Schmidt's "E6" version of the Bisy (see below) can be so equipped. These lights have suitable contact arrangements so as to permit the use of a tail light with them. Switched headlamps certainly decrease the weight and wiring complexity over a separate switch, but obviously lose the ability to have a switch on the handlebars with a light mounted in a more suitable position such as the fork crown.
If you want really impressive headlights you can fit a secondary headlight in series with the primary headlight (and taillight) - this would normally be a 3W light, although I see no reason why it should not be 2.4W with a secondary taillight in parallel. This light needs a switch of its own, because the two lights will not become bright until twice the speed at which a single light does, and that speed is low enough that one might realistically be under it uphill - my single light is bright at about 6mph. This switch is differently wired; it shorts out the lamp rather than opening the circuit, and so if a lamp with integral switch is bought it must be explicitly wired as a "secondary" - however, this implies that an integral switch secondary will work in parallel with a tail light. However, you are going to want to flip the secondary switch quite often, and that would suggest it must be mounted in a convenient place. In a twin-headlamp setup one would normally mount a standlight-equipped primary, but use a Bisy (or E6) as the secondary, since it appears to be the best headlight available.
Personally I don't see much point in a twin-headlamp setup. It still has a single point of failure, so a prudent cyclist will still want to mount a backup battery headlamp, obviating the need for a standlight; and if one doesn't need a standlight, a single Bisy headlamp provides more than adequate light for any on-road riding.
Schmidt make versions of the Bisy lamp with a metal body and integral switch for use as both primary and secondary lamps, the E6 and E6-Z - however, they cost 60 pounds instead of 20. They also make these without the "signal ring" - the doughnut of plastic around the edge of the Bisy that glows brightly, and while this is handy to see if it's on when mounted on the forks, it could become dazzling when mounted on the handlebars.
So, what's it like? I find the Bisy amazing, putting the battery lamps to shame - and the halogen bulb battery lamp has a nominally higher power output - presumably because the beam pattern of the Bisy is very well designed. It projects a rectangular beam forwards which forms an isoceles trapezoid on the ground; with the light horizontal, the top of the beam is apparently horizontal, and the base of the beam is about 6' in front of your front wheel. There is some scatter - not a great deal, but enough that you can see that last 6' of road if you want to. It simultaneously does a better job of illuminating the road surface than the halogen bulb lamp does (which I have angled downwards to provide light from about 10'-30' out) and of sending light fowards to illuminate upcoming road signs and alert oncoming cars than the LED light does (which I mount horizontally) - and, of course, there isn't a gap between 30' and the horizontal. The signal ring on the edge of the Bisy also appears very bright, which presumably provides some protection against idiots hitting you in the side.
The lamps are bolted onto the bike, and the hub comes with an allen key skewer, so stealing this equipment is not entirely trivial.