I've entered Edinburgh Marathon, which is at the end of May.
I'm no expert by any means but a friend who has written a lot of training plans for a lot of people and managed to recently get all 5 of his 'pupils' to smash their PB's at Berlin marathon hasn't got me doing proper speed sessions until mid March.
My training plan starts next week and includes fartlek sessions fairly early on (from week 2) and either 3 or 4 runs a week (as I'm prone to injury). By the time I start the real speed sessions I'm already running 14 to 16 mile long runs.
He may have done this becuase of my previous injuries but I totally trust his judgement so I'll be sticking with it.
I also have small girly wrists and use the fabric strap on my Garmin Forerunner 410. I tried on quite a few options before I went for this one and a lot of the bigger models were uncomfortable on my wrist.
It has had a few bugs but generally these stop when I update the software.