One of my bikes has an ISP and I don't regret it. The biggest regret would be if you cut it too short, so don't. Since you don't care about resale, it's only important that the bike fits you. Most ISP bikes have a small amount of adjustment in the design to account for differences in saddle and pedal stack heights.

The only other problem I can think of is that an ISP frame may not fit in a bike case for traveling/shipping.