Solid State Disk for a desktop computer [closed]

"Do they not come in desktop sizes?

The only ones I've seen are 2.5"". You can use mounting brackets that allow them to be mounted in 3.5"" bays.

Can they be purchased at a resonable price now?

The Intel X25-M Mainstream SSDSA2MH160G2C1 2.5"" 160GB SATA II MLC Internal Solid state disk (SSD) - OEM is USD 579 @ newegg (ATOW). If $579 for a 160GB SSD is reasonable for you, then go for it.

Are they worth it?

The Intel X25-M is $3.6 per GB. The VelociRaptor from the graph below is $0.76 per GB. You're paying 4.7 times more per GB for this SSD, and the speed improvement is 2.4 times faster. The hard drive is a known bottleneck for most systems so 2.4 translates to a huge performance increase across the board.
Pros

Extremely fast (transfers and random access)
quiet (no seek noise, no idle noise, no vibrational noise)
slightly less power usage
less heat

Cons

very expensive cost / GB
drives are relatively small and may require an extra drive for large storage
The wear-leveling issue. Over time the drive will slow down b/c of the algorithm that tries to prolong drive life by distributing writes evenly across all bits. Anand still feels that the speed loss is not enough to deter him from recommending SSD's though.
3 year warranty vs 5 year for many rotational disks

notes:

Tests by anantech, The SSD Anthology: Understanding SSDs and New Drives from OCZ"

"An additional thing to consider would be that SSDs have no moving parts, so will not fail because of a head crash or from a motor breaking down.

Note: A good backup system means that recovering from a hard disk failure isn't a major problem anyway.

Whether the disks are worth buying or not will depend on how you break down the costs and benefits.

Price ($): SSD is more expensive per GB than a standard HDD
Reliability: 2.5"" drives these days seem to be very reliable
Power Consumption: You said that this is a desktop computer, it's plugged into the wall... though you may be building a system based on an Atom Processor and working to save as much power as possible (I don't know).
Lifetime: SSDs have a limited write cycle, however OSes should be more SSD friendly in the near future... Up to you to decide how much of an issue this is.

What's cheaper, your time, or electricity?

If the electricity is cheaper, then maybe you should go for a more power hungry computer (and power it off/unplug it when it's not in use to save power).

At the end of the day, you are the one that knows the conditions that this machine is to be used in, and how it's likely to be used. Good luck in making a good decision.

Tim"