I like to remind people that keyboards (and mice) are extensions of our own hands and fingers. As such, you really need to go play touchy-feely at a computer store and find out what "feels" best at your finger tips. What feels great to me may feel awkward or even painful to you. And the fact you are already complaining of finger strain makes that advice even more pertinent.
We can comment about build quality, travel, noise, features and stuff like that. But feel is totally objective.
I will also point out there are other factors that come into play. Do you want wired or wireless? Do you have limited space and therefore need a compact keyboard? Or are there no size limitations? Do you want contoured or flat? Ergonomically curved or straight? Does it need a number pad?
And as bonehead123 asked, what will it be used for?
I have 3 of
these Microsoft Wireless Comfort Desktop 5050 keyboard and mouse sets and love them. I don't know who makes them for MS, but I bought the 2nd two because I liked the first set so much. It is flat, but as you can see, curved to allow my wrists to stay aligned with my arms as they approach the keyboard (a big problem for me and smaller strait keyboard - like found on notebooks as I have carpal tunnel and
RSI issues from decades of typing. This keyboard made the wrist pain, tingling and numbness go away - staving off surgery, hopefully indefinitely!
So, is an ergonomic keyboard important?
And the ambidextrous mouse is great for me because while right-handed, I use the mouse with my left hand.
And since it is a set, it uses a single wireless USB dongle for both keyboard and mouse - meaning only one USB port is used for both. While not a problem for home users, the AES 128 encryption is nice too - good for those worried about bad guys picking up your keystrokes with a wireless keyboard.
I do, however recommend rechargeable batteries when using these wireless devices. Depending on how much you use your keyboard, the batteries need to be replaced every 4 - 6 months (at least on this model).