We live just off Cann Hall road, been here knocking on for 20 years - and we absolutely love it.
Good Points:
Cheaper than other, more 'established' bits of Leytonstone (IE Bushwood and so-called Upper Leytonstone).
Housing stock is typically (and almost exclusively) two or three-bed Victorian terraces, with a garden and useful front yard. They make great family homes.
Quiet and safe.
After years (decades) of being bedsit-and-quick-turnover-rental land the area is being 'resettled' - lots of families have moved in, and the streets are becoming gradually better kept. Some 'newcomers' have spent a lot of money and time doing up their houses, removing stone cladding and replacing sash windows, etc. Some properties now look very smart indeed. When we got here, the area around Cann Hall was very run down. Now, It actually feels loved.
I'm not exaggerating when I say I know all my neighbours for about 7 households either side and opposite. It's a friendly place. We look out for each other.
It's a doddle to get into Central London. The 58 bus runs to Leyton station. The High Road is a short walk for buses to Zone 2 Stratford or Zone 3 Leytonstone 'proper' (Leytonstone is a short walk in any case). Maryland and Forest Gate (which are getting Crossrail) are nearby. I often cycle to work at Aldgate - an easy 30 minutes via Olympic and Victoria Park.
Spoilt for choice for open spaces. Wanstead Flats just around the corner, Olympic Park an easy bike ride, bus or walk away. Victoria Park a bit further.
After years of nothing but chicken shops and (mainly) stabby pubs, Leytonstone is undergoing a bit of a transformation - and as others have noted, it's creeping down the High Road. The lovely Lake House Cafe opened a few months ago, as did Chef's Corner bakery/cafe. There's also the brilliant Wanstead Tap and Hawkes' Cider on Winchelsea Road. The Rookwood Tavern is to reopen as one of Antic's pubs. There's also a lot going on at Forest Gate, a 20 minute walk away. Hackney Wick is the apex of grooviness at the moment, with all the cool bars and restaurants you'd ever need - and that's within easy reach (eight minues by bike - i've timed it).
I could blather on for hours about the good points - but you need to know the bad points.
Cann Hall Road is a racetrack. Standards of driving are woeful.
Flytipping is a problem - but not unique to this area. Litter (especially beer cans) and dog crap, ditto.
Parking is free (rumours of a controlled parking zone being introduced) - which seems to attract a number of long-wheelbase white vans taking up two parking spaces. You'll be lucky to park outside your home.
Hope this helps - any more questions, do ask. A best of luck.