If memory serves well, today makes the sixth month since I have got my MacBook Pro and, during this period, have been using it as my sole computer. I feel it is a good time for another mini-review.
Well... to get started: this machine is great; I probably haven't been happier with any other computer before. I have been able to work on real stuff — instead of maintaining the machine — during these months without a hitch. Strictly speaking I've got a couple of problems... but that was "my fault" for installing experimental kernel drivers.
As regards the machine's speed, which I think is the main reason why I wanted to write this post: it is pretty impressive considering it is a laptop. With a good amount of RAM, programs behave correctly and games can be played at high quality settings with a decent FPS rate. But, and everything has a "but": I really, really, really hate its hard disk (a 160 GB, 5400 RPM drive). I cannot stress that more. It's slow. Painfully slow under medium load. Seek times are horrible. That alone makes me feel I'm using a 10 year-old machine. I'm waiting for the shiny-new big 7200 RPM drives to become a bit easier to purchase and will make the switch, even if that means my battery life will be a bit shorter.
About Mac OS X... what can I say that you already don't know. It is very comfortable for daily use — although that's very subjective, of course; it's quite "funny" to read some reviews that blame OS X for not behaving exactly like Windows — and, being based on Unix, allows me to do serious development with a sane command-line environment and related tools. Parallels Desktop for Mac is my preferred tool so far as I can seamlessly work with Windows-only programs and do Linux/NetBSD development, but other free applications are equally great; some worth of mention: Adium X, Camino or QuickSilver.
At last, sometimes I miss having a desktop computer at home because watching TV series/movies on the laptop is rather annoying — I have to keep adjusting the screen's position so it's properly visible when laying on bed. I can imagine that an iMac with the included remote control and Front Row could be awesome for this specific use.
All in all, don't hesitate to buy this machine if you are considering it as a laptop or desktop replacement. But be sure to pick the new 7200 RPM drive if you will be doing any slightly-intensive disk operation.