I have one, mainly because I lack the skill necessary to build one of my own. In terms of time, effort and frustration, the cost was worth it to me for not having to go through the anguish of self-build. As to your questions:
- How durable is it?
Seems very sturdy, although the clips used to clip the tiles together seem somewhat fiddly
- How easy is it to store? (I know it is 6 2X2 foot pieces, should fit easily into a closet or under a bed) I recently bought my own house and am lucky enough to have a dedicated gaming room that I negotiated with the misses. So mine is permanently assembled.
- How easily is it painted/modeled? For a modelling slow like me; surprisingly so. I followed Panic's guide:
http://www.dakkadakka.com/wiki/en/Terrain:_GW_Realm_Of_Battle_Board:_Standard Adapted it slightly for my own ends - with the wife's help , it took 2 days.
- Does it get boring quickly? I'm inclined to think not since there are enough combinations for me and I use terrain to create the variance rather than geography.
- If you do have one (or a similar board system) how often do you use it? I use nothing else. My advice would be, if you have the money to spare, then go for it.