I started my mechanical keyboard search (or journey?) on an IBM Model M, but it was a little too stiff and big for me. I now use a Leopold Otaku tenkeyless (https://elitekeyboards.com/products.php?sub=leopold,tenkeyle...), with Cherry browns. I wasn't sure which Cherry switches to get, but from doing some research, people seemed to agree that Cherry brown switches were good for all-around keyboard use (gaming, typing, etc.). While I like my MS Natural 4000 (especially for the leatherette wristpad), I really enjoy typing with my mechanical keyboard better.

I would also recommend a key sampler, as @wattson mentioned.