The main appeal is its user friendly touch screen interface and perhaps convenience...the fact that you can buy all the music server components in a single product line.
I'm finding though that with a decent DAC, it is not hard to get very good sound for not much cost.
I'll do that when the time is right, I'm keeping a close eye out on the market. There are lots of super buys at places like Micro Center where they sell a HP or other laptop at a screaming deal and you just add a Buffalo array and DAC and good to go.
I'm an Apple guy, so it would be even easier for me if I could snag a good deal on one of their laptops.
I still think touch screen is just a heartbeat away, I saw an HP ad on TV the other day that had the feature, so how far behind can the rest of the guys be?
Once the super user-friendly touch screen is common, the market will be flooded with cost busting options to do it yourself with a server.
Here's the HP demo at YouTube. I've not tried it in person but it sure looks flexible and it's really easy on the eye too.
HP Touchscreen