Personally I adore boa's, specifically the colombians. For me the list would look like this...

Pros:
- realitively easy keepers
- not terribly prey specific
- generally a very good prey response without a tendency for refusals
- not as easily stressed as ball pythons
- responsive to correct and appropriate handling
- laid back temperment (for a snake)

Cons:
- too available in pet stores so often not a "quality" snake so best to get from a good breeder
- females can get large so confirmed gender is important to some owners
- larger snakes need larger enclosures
- very strong at maturity so appropriate and safe handling is a must
- very long strike range so smart feeding methods need to be learned
- able to carry diseases that kill BP's so health history must be known at purchase (impossible in a pet store purchase)

I think a colombian boa makes a wonderful pet snake if one does the research you should always do and is prepared for it's size at maturity. These aren't giants by any means but if you don't respect the sheer power and strength of a mature colombian boa, especially the bigger females, well you're ten kinds of a fool.