Keith Marshall wrote the following on the forum (thanks Keith):

Honest reply? You'll get more bang for your buck with a Linux (or FreeBSD)
box, for the kind of thing you're trying to do, in the short term at least.
You could even run Solaris for Intel on it, so it would be more flexible.

 But, there are some pros of buying a Sun:  1. It'll last longer than most PC 
hardware, certainly than the cheaper end of PC hardware, and maintain it's 
usefulness

2. It will do everything you need for development, although it might
possibly be a bit slower than a Linux box at the same price.

3. It may help considerably when it comes to applying for jobs - knowing
your way around a Solaris box has serious kudos in the industry and will
make you stand out from your peers who only know Linux. Solaris sysadmins
tend to be well paid :)

4. It will *never* crash or hang.  I own a Blade because I need to develop 
software across multiple platforms, and I needed something to run Solaris 8 
in full 64-bit mode. My old Sparc2 was getting a bit long in the tooth (it 
still works very well but it doesn't support solaris 8 and it's sloooww!). 
The Blade 100 is pretty good value for money compared to any other Sun kit 
I've ever seen, particularly when you can just buy a base system then add 
cheap third-party memory. I also have a couple of PCs so that I can run 
various versions of Linux and Windows for the same reasons. I'm beginning to 
use the Blade as my main development platform just because it's stable and I 
can rely on it never dying on me without warning, which I can't do on any PC 
hardware I have (none of it is expensive stuff). I still use Windows for 
trivial stuff like surfing the web, reading email..

I've just paid 70 UK pounds (about $110) for two 256Mb ECC DIMMS from Crucial.
Turns out these are Micron DIMMs and identical to the 128Mb DIMM already in my 
Sun Blade. Heaven only knows how much Sun would have charged for the same 
memory.. and it sure makes the machine run more smoothly.  I can't answer your 
question about the 3D stuff though - the chip in the Blade should do some 3D 
but I don't use that kind of application so I don't have any benchmarks. The 
lower spec graphics chip will still drive a monitor at 1600x1200 so resolution 
isn't a problem. Again, I'm not using a Sun monitor but a cheap CTX 19" at a 
fraction of the price. 

 Hope this helps, Keith.

If you have a reason to use Solaris (eg. you develop on SPARC or you need to 
run a commercial application under Solaris) then you can probably find a good 
case to have a Sun Blade 100. I use mine to run Oracle, some application 
servers, and to investigate networking ideas.

In my personal opinion, Linux is easier to use and more intuitive than 
Solaris. Also, the hardware base cost is always going to be lower on Intel 
(bang for buck etc.). I don't feel that it makes sense to buy a Sun Blade 100 
to "improve" on Linux, unless you have other interests in the Sun/SPARC 
platform and can resist spending the cash on a more powerful Intel solution.