The beam of the P7 is a central spot with a large corona (?), though in use on the bike, only the spot is visible.
Versus any HID lap I've seen (Hope/lupine/Lumi), the P7 blows them away, all of a sudden the HID output seems useless....
My m8 strapped one next to his Hope HID last ride, and the back garden test... shining onto a row of leylandii around 15 ft away, the HID gives a large area of illumination (say 10ft across), with the P7 on, this area is totally overshadowed by the P7's bright central spot.
The HID is competely redundant - well I definitley won't be buying another or even getting mine repaired when it eventually breaks.
I think to get the best out of the P7, it needs to be head mounted, so the spot is specifically where your looking.
Thats a solid P7 model you've linked to IMO, it's the one I like, as the medium beam setting is very useful.
A lot of ppl do recommend the 2 mode http://www.dealextreme.com/details.dx/sku.12325 and it is slightly cheaper.
If you going to cut and shut i, I think you'll be doing away with the switch, so the 2 mode would do the job.
I've not seen both (2 & 5 mode), but I believe the only difference is the switch.
The other torch I've tried is this MC-E LED version:
and I totally disagree with Stevemorg2's report... my MC-E gives a 1/3 larger spot IMO, though is no more powerful output wise.
Though the thread/end shape on the switching unit is different to the P7, so the P7 stuff being developed on here won't fit it... if your plans are to go that way, avoid this lamp.
(also the 8 modes are a nightmare to use, if you switching mid-trail).
I demo'd both types to my friend, and he bought the MC-E version (the P7 was already sold to another m8).
One final question, why not use the Li-Ion batteries, there dead cheap and pretty damned good... an hour a battery on full beam - you surely won't get anywhere near that with a AA (not that I know the math)