"Used it for 2 months and have no complains."4.5 starson by staworko
Pros: Great OS, ample CPU, improved graphics, very compact, quiet and very "green".
Cons: RAM upgrade necessary (at least 1GB more)
Summary: I considered buying a Mac Mini for quite a long time. Its reliable and easy to use operating system was always very tempting. However, the lack of good graphics was too discouraging. The recent upgrade to NVIDIA 9400M chipset left me no more excuses.
What I use it for: web browsing, document preparation (PDF, TeX, etc.), programming (UNIX-like system is a big plus), and occasional movies and games.
I'm a typical switcher: I already had a very good monitor and all the peripherals (used with an Acer 5570z laptop). The computer comes in a small package, is very easy to unpack and install. I knew the Mac OS X system from work so my experience with Leopard was a bliss from the very start.
I was very pleased with the performance of the Mac Mini. The NVIDIA 9400M performs very well. No problems with playing movies. Most of the games that I tried work quite well (UT2004 is very fast, Quake4 at 800x600 is still very captivating). It's clearly an entry-level chipset and it uses a shared RAM (DDR3 nonetheless). I have no problem believing it performs 5 faster than the Intel GMA 950 used in my previous Acer laptop. However, it comes without saying that if you're a gamer, getting an iMac, MacPro, or MPB might be a better idea.
The only problem I had with the default configuration was the RAM size. I soon realized that 1GB of RAM was too small. In fact, with only 1GB the system has a difficulty getting all the power of its two CPU cores. For instance, while decompressing a large zip file (a process which can use up to 99% of one core power), other applications (Firefox, Mail, etc.) became very unresponsive. The problem was resolved with a memory upgrade. I've upgraded the memory myself, and although more challenging that upgrading memory in most laptops, it wasn't as difficult as some describe it.
I've heard a lot of complains about the hard drive: limited capacity (120MB), slow speed (5400 rpm and one plater only). I find its performance quite ample and prefer to look at the whole thing as an easy way to boost my Mac's performance in the future. Compatible, faster drives (7200rpm) with larger capacity (up to 500GB) are already available, but are quite expensive (in one year I expect the prices to come down).
Finally, there is something to be said about having a Mac: it's a classy computer. Not only it has aesthetically pleasing looks, but it's also very quiet and green!