If and when Nikon comes out with a bunch of f/4 semi-pro zooms, I may not need Olympus anymore.
I would love to see something in that genre from Nikon. The 16-85mm f/3.5-5.6 is a great start though. It seems to have above average performance. It's hard to tell with the latest, new lenses though. Everyone invariably raves about it or condemns it - you don't see a lot of carefully considered opinions.
ddreuding,
I know you've got Canon gear (a great choice by any standard), so what I'm following up with may seem superficially irrelevant, but I'm doing what e_dawg did, trying to explain my thought process. It might hit something that'll make a light bulb go off, but if not, I just want to demonstrate how you want to work backwards from a set of circumstances to determine what gear you should look at (particularly for your 2nd camera). Work backwards... don't think about how gear will augment your capabilities - (nearly) every single lens & body out there has something it's great at. You need to think about what you NEED from it...
For me, I had two separate needs.
1) I wanted a camera for candid portraits indoors.
My biggest consideration here was getting some outstanding portrait lenses.
I needed a lens that could get a close headshot at a comfortable and discrete distance, and I needed a wider lens that could take environmental portraits, and group shots. I ended up going with Pentax because their legendary 31mm & 77mm limited primes were right in the focal range I needed on a crop body. Their out-of-focus rendering was also beautiful - a consideration that was crucial to me. The 31mm in particular is standout in this respect. Not in an absolute sense (since I'd say the 77mm is even better), but relatively. Most wide-angles -even mild wide-angles- have at best mediocre performance when it comes to rendering the out-of-focus areas and at worst, distracting, ugly bokeh (all too common). In contrast their are a lot of nice rendering lenses in the range of the 77mm. The 31mm though, is all alone (among AF lenses anyway).
As with e_dawg, in-body shake reduction was also a big factor. Since I was going to be shooting with primes indoors, in low light I needed the SR in the body.
The competition that the Pentax won out over was a 5D w/ a 35mm f/1.4L & a 135mm f/2.0L. It's still a very close call in my mind, and I won't get into all the nitty gritty, but obviously I went with the Pentax (cost was not a determining factor).
2) I needed a body & lens for hiking & landscape work.
I go on extended, multi-day trips so I think the decision-making process could very well be different for people who only do day hikes.
My dominant consideration here was high-quality lenses for landscape photography, but this didn't narrow the field a whole lot. At f/8 to f/16, there are differences but everyone can cover the ranges well at those apertures.
Size, weight & range did narrow the field somewhat. Olympus has a spectacular selection here. The 12-60mm & 50-200 are completely unmatched. The 70-300mm is a great option if you want more reach. No one else provides such a complete range, with such good IQ, weatherproofed, in those sizes & weights. Canon's 24-105mm (an excellent lens) is the closest to the 12-60mm (and it was a real contender).
Weather-proofing was also a huge item. Olympus was again at the top of the heap. The only issue was that, when I was buying, the E-3 was not available (nor announced). Pentax offered the only reasonably-priced weatherproof body in the K10D, and, since Pentax was at the top of the list for my other criteria, everything seemed to come together. So, I got a 16-50mm DA* as a weatherproof standard zoom. I wish
very strongly that the 17-70mm f/4 & 60-250mm f/4 were weatherproof (but wishing does not a single rubber seal make).
Today, I'm very tempted by the Olympus option. They seem to be the only one that understands that there is a subset of photographers who want phenomenal optics, weather sealing, range, & reasonable size & weight, and who don't need f/2.8! You wouldn't think it's rocket science, but apparently it is.
Where I'm going:
Like e_dawg though, I also love Nikon's CLS... And I have to admit Canon has some fast primes, and great low noise performance in the 5D...
As I said, all the equipment out there has its own siren call. At some point you have to prioritize even if not for the sake of your finances, for the sake of whatever shoulder you carry your camera bag on! To do that, you have to think about what you shoot, and not about the one or two shots that got away, but what you shoot 99% of the time. What gear is going to make taking photographs more pleasant/simpler/more enjoyable.
P.S. Personally the Xti viewfinder and single control-wheel layout would drive me crazy. I also need at least a little weather-sealing. I'd go with a 40D.