Monsters are good all round bikes,I went from a 916 to a monster750 and thence to an S2R and am quite happy with my choice.
Like all things it'll depend firstly on your budget and whether you'll want the water or aircooled engines,and how new or old your bike may be.
They are probably the most modifiable bike out there,easy to work on and bits are easy to come by.
Have a look here:-
http://www.ukmonster.co.uk/monster/index.php you can get pretty much all you need to know from there.