Crucial M500 SSDs support self-encrypting drive (SED) technology which allows BitLocker for Windows 8 to simply be used for encryption key management rather than software-based encryption.  Out of the box, the drive encrypts all written data and decrypts all read data - and functions like a non-SED drive until key management software like Windows 8 (and Server 2012) BitLocker is used. [more]

When you turn BitLocker on using Windows 8 and a compliant SSD like the M500, you don't have to wait for the whole disk to be rewritten and it's encrypted.  Thus, you can encrypt the whole drive in a couple of minutes or less.  As far as BitLocker and Windows is concerned, it functions just like traditional non-SED drives do regarding pre-boot passwords, recovery keys, etc. 

An interesting spec is Crucial states their SSDs are designed to support 72TB total bytes written (TBW) - which is equal to 40GB per day for 5 years.  It stands to reason that if you don't have to rewrite every byte of an SSD when you use BitLocker to encrypt or decrypt the whole drive, it should help the life expectancy of the drive. 

So, since the drive I/O specs include the hardware encryption overhead, you lose no performance whatsoever when you implement whole disk encryption using BitLocker for Windows 8 on these drives. 

A very basic description of Crucial M500 encryption can be found at

http://forum.crucial.com/t5/Solid-State-Drives-SSD-Knowledge/An-introduction-to-the-encryption-features-of-the-M500/ta-p/128272 

More specs are available (since this is a Micron drive) from:

http://www.micron.com/~/media/Documents/Products/Data%20Sheet/SSD/m500_2_5_ssd.pdf