If skill gain didnt mean it would take me months to get back to where i am now with my chars (for the next 6 months i will be lucky to have more than 30 mins a day, avg, to play) i would gladly play siege.
But, considering the time it takes to start a new char (takes long enough on prodo shards to get to 120), i just dont see myself playing siege ... Housing would also be an issue.
No, i think if they opening up a *small* (small tower largest option for 2nd house) extra house per account on siege/mugen, you would see a lot more of us giving it a whirl. =)
-LoL