DLNA is a standard for file sharing, but the device you use to access it is going to be a significant factor. Lots of DLNA-compliant devices exist, each with different capabilities for audio files, image files, and video files. FLAC is probably the logical choice for lossless audio, although there are some other options (lossless WMA, Apple Lossless, WAV, ...).

If you do the Squeezebox, one advantage is that it is fairly turnkey. You have to rip all your CD's, but the rest of the setup is straightforward - use the software they provide, and away you go. This is similar to the AppleTV, which is also locked in to one software package (iTunes) and one hardware platform. The AppleTV can be controlled from an iPhone or iPod Touch, which is good because the AppleTV remote has barely half a dozen or so buttons (far too few to be truly useful, in my opinion).

When using DLNA, you have more choices - and thus more decisions to make. Most of the DLNA servers are Windows apps. Some are free, while others will cost you some money. Features vary, as does performance. You also have to decide on a network player. DLNA devices have been growing steadily more common. There aren't a lot of standalone DLNA clients, but it's part of a lot of TV's, surround receivers, game consoles, and BD players. The OPPO Digital BDP-83 and BDP-80 disc players both offer some DLNA support, but can't support any lossless audio formats (which makes them less than ideal for this sort of application). There are rumors that the BDP-93 will offer more capabilities in this regard (possibly including FLAC), but we won't know for sure if that really happens until the player is received (possibly in November or December).