Put it like this; your keyboard and your mouse, no matter how you look at it, are the two things that you use the most on your computer, period. If you do any kind of normal office work, you will find that the thing you use the most by far is your keyboard. So yes, spending however much money you feel is right to get a great keyboard is a must, I'd say. If you like laptop style keys, your best choice overall is probably the Enermax Aurora (however, I'd not recommend the Premium model; it has a small delete key and a right-shift style Return key, ridiculous for a keyboard that is going to be sold in the UK market). At £50, it might sound rather dear, but comparing it to the Logitech Illuminated that people have been raving about recently (which almost certainly will no better built than the Enermax, and no better to type on), it's a good deal. The keys are solid, weighted nicely, and the whole thing overall is beautifully made.
If I was workin in an open office I would get the Silent version for my desk and the Ultimate version for home. This way, your colleagues won't murder you As an example of reliability I recently poured half a liter of water in the keyboard and it kept working.
I have the same keyboard as you... life it, see how heavy it is.. see how it's high quality stuff. Also Logitech service is also excellent. I had my MX Revolution break some time ago... the mouse was randomly double clicking. I called Logitech, no wait time, they asked my name, address, product in question, I explained the problem, and I said I already tried to re-install the SetPoint, and they said no problem, he asked the PiD number found under the mouse, and said they will ship a new mouse, with everything included in there (retail box). I ask if I had to e-mail or fax my bill or send the old mouse.. they send no, it's not needed, I can trow away the current mouse as soon as the replacement mouse arrive. The whole conversation was FAST. Best service I ever had in a company. 3 days later, I got my new mouse, and indeed it was a new MX revolution retail box. I read countless of stories from Logitech service including people that were able to replace there whole surround sound system despite being out of of warranty, without sending to Logitech anything. I heard that sometimes, depending on the situation they actually might ask the bill, but in such case it's easy to, and not problematic like in sending your old broken product to them. So you pay for this premium service as well.
Hmm... no ergonomic users here? I'd say that my MS Natural Ergonomic Keyboard 4000 was well worth the money (~£30 now, was more). Takes maybe a week to get used to if you don't use ergonomic keyboards, but aside from being infinitely more comfortable, it actually 'taught' me to touch type. Buying quality peripherals is a good investment... and something that any computer receiving regular use should have, imo.
It depends on you.. usually people with wide shoulder prefer ergonomic keyboards.. those you don't, well don't, and prefer the normal keyboard form factor. Also, ergonomic keyboards are usually tend to be on the noisy side, when typing.
My current typing 'board is a Goldtouch butterfly-style, which like yours also helped teach me to touch type.
The No.1 priority has always been to get the PC box working and then grab any old keyboard/mouse to plug in. After reading all your posts I'm starting to feel a little easier over the purchase. I know when I see and use it I'll think it is money well spent. I may just get the Logitech M1115 mouse to go with it (£10) for now. Having always used old, second-hand loud PCs I built this one with low noise levels in mind. I paid £20 extra for the Vapor-X version of my GPU for cooling and quiet, I bought the Coolermaster PSU for low noise levels and I got the Artic Cooling because it would work better and quieter than the stock fan. Now the loudest part of the PC is my girlfriend and her rants, "If that mouse squeaks once more I'll put it where the sun don't shine!" and "Can't you ****ing type any quieter?". Once the Logitech keyboard is delivered my low noise level PC will be complete with the loudest part still being my girlfriend, "You spent HOW much on a stupid keyboard?"!
£30 for my Saitek Eclipse II was well worth it, lovely quiet action on it. £45 on my CoolerMaster Storm Sentinel mouse was worth it too, I don't think I could deal with no on-the-fly DPI adjustment and a little screen to show what level it's on anymore. I reckon that you need to spend money on your input devices otherwise your uber-expensive rig will feel cheap, no matter how awesome the visuals it can produce. That said, I did use an OEM Compaq keyboard and the basic MS optical mouse when I started gaming and they did work. They don't compare in terms of feel to my current stuff however.