Surely not the worst 'brandable' ever, being a LLLL with a good keyword makes it better than some, a certain amount of rarity with no other [L]bet.co.uk domains available, but definitely more of a speculative register.
Fbet/com sold at Sedo for $1250/£600 in Nov-07, but that was both a LLLL and .com, with international appeal.
[I/S/V/M]bet.co.uk are all on sedo, with I/V/M having received bids, obviously more value with ibet, so I guess its a case of listing it and seeing if there is any interest.
Not much value at the moment in resale terms as has already been said, but one for longer term hold, may gain more value as & when LLLL.co.uk's are no longer ftr.