Well, I am hesitate to ever recommend to someone to use a proprietary technology to archive information. WMA lossless is owned and licensed from Microsoft. I'd rather not have my music library locked into this. If someone wants to come up with their own conclusion, it's their choice and as long as they knew the pros and cons, I have no problems.
Secondly, FLAC is supported as much or more than WMA lossless. There are portable players and for home network playing, squeezebox has long supported FLAC and has had to transcode wma lossless due to license fees.
Lossless is lossless. It's the exact audio copy of the music. However, how that is store for future needs is something I would consider when choosing what format to go with.