The pros and cons of off-set Mortagages

Angelfalls_2

My fixed rate mortgage of 4.99% with Northern Rock is about to come to an end and I am considering getting an Offset motgage with First Direct at 5.29% fixed for 3 years. First Direct has been my bank for the past 12 years and they have been great so I wouldn't consider moving my current account. I have about £2k in savings at the First Direct rate of 5% and there is about £3.5k going in and coming out of the account each month. I would also play the credit card game and get a 0% on purchases CC and keep that money in the account until I have to pay it off and start again or balance tranfere. In his mortage articles, Martin doesn't seem to be very keen on off-set mortgages but I would really like to pay my mortgage off early and think this would be a good way of doing it. What does anyone think? Many Thanks in advance