XFS & Btrfs For Linux 3.16 Bring New Features

[anybody]

Is Btrfs already reliable for network storage systems? I read somewhere that it was not reliable yet for RAID based systems, and ZFS was recomended instead (using *BSD in place of Linux)

Only RAID 0/1 is supported, RAID 5/6 is still highly experimental (lacking basic stuff like rebuild functionality). That is not a secret though and stated plainly in the btrfs wiki. Unfortunately not much progress (if any?) regarding RAID 5/6 in the last few months so I don't know if this will change anytime soon.

However, SSDs perform compression internally to reduce flash writes,

Of all the SSD controllers on the market, only SandForce uses compression internally. Your generic statement "about SSDs" is completely wrong.
Also, while SandForce had quite a market penetration some time ago, currently the vast majority of SSDs is NOT SandForce based and does therefore does NOT use compression.

so you may gain a bit more disk space, but you lose drive lifespan as it has to write more data to the flash.

If the data is precompressed that will not make the drive write "more data", you will just lose the advantage that a 100% full drive has still a lot of spare sectors (useful to retain write speed and reduce write amplification problems).