If looking for a commuter - buzzing round town - the 600/620ie - is ideal.
However, if having a blatt out of town, (with other bikes)you may find that the 600/620 is having to work quite hard - I know the guys who ride on the monster meets comment on this sometimes.
Why not try the 750 (ie)/800/900/1000ie's?
I find my 750ie is ideal for town & country - has to work very hard to keep with the likes of Blackbirds & 998's - but we do try!

No real probs to speak of with the newer monsters (isolated mechanical probs on forum feedback only) - except sometimes a great deal of aggressive corrosion - again in isolated cases (mainly on 2002 bikes it appears)
Best of luck!
If free - why not pop into the UKMOC 1st annual 'bash' - at Arrow Mill on Bank hol w/end - if you get there on the Sunday about 10am, you will get to pick the brains of about 60-100 - going on the 11am rideout

CK